R/B/Y
(I didn't know what the *s meant.....)
High
Bulbasaur - It's a starter and is good for absorbing poison in Viridian, it makes mincemeat of the first four gyms.
Charmander - It's a starter and is horrid against the first two gyms, but shines later on due to high Speed and power.
Squirtle - It's a starter, its usefulness fluctuates depending on where you are in the game, it's slow but powerful.
Spearow - Easy to find and train, good Speed, and it can use Fly.
Pikachu - Rare in the Viridian Forest but it's good later on.
NidoranF - Great movepool and stats.
NidoranM - See above.
Diglett (+Dugtrio) - Fast, powerful, and handy for attacking.
Abra - Hard to get and evolve but nothing compares in Speed and Special.
Geodude - Good stats and power later on, but it's slow.
Doduo* - Bit harder to get, but it's as good as Fearow.
Staryu - High Speed and Special makes it worth getting, but it's obtained late.
Mr. Mime - A handy pokemon with a great movepool.
Snorlax - Very hard to catch, but has great stats.
Zapdos - See Snorlax, but with a better movepool.
Mid
Caterpie - It evolves very fast but it's weak later on and has poor stats and a shallow movepool.
Rattata* - Hyper Fang is good later on, but it's weak overall.
Sandshrew* - Decently powerful and easy to find, but it's slow and frail.
Clefairy - Very rare and it needs TMs to be effective.
Jigglypuff - Sing is good, but it has low Speed and power.
Oddish - Great movepool and it's easy to find, but it has no power and is annoying to train.
Meowth - Fast, decently powerful, but it's hard to find and needs a TM or two.
Psyduck* - Not that hard to find, but it's annoying to train for little reward.
Mankey - Its good stats are let down by a poor movepool.
Poliwag - Decent power, but it's hard to train and needs TMs.
Bellsprout - Very annoying to train with low power and Speed despite a good movepool.
Slowpoke* - Has good bulk, but it's slow and annoying to find.
Farfetch'd* - By the time you get Farfy you should have better options.
Gastly - Fast and powerful, but it needs TMs and it's obtained late.
Drowzee - Good movepool and okay stats, but it's annoying to train.
Exeggcute - Hard to get, obtained late, but it has a decent movepool.
Rhyhorn - See Exeggute.
Jynx - Bad stats despite the good movepool, hard to find
Magikarp - Takes way too long to train
Lapras - Obtained at such a low level it's not worth training
Vaporeon - Has a good Special stat and bulk, but its movepool is lackluster.
Jolteon - See Vaporeon with less bulk and more Speed.
Articuno - The first legendary you can catch, don't waste your Masterball.
Low
Weedle - It evolves quickly into a pile of garbage.
Pidgey - It's weak, slow, and a one-trick pony.
Ekans- It's rare, weak, and has a poor movepool.
Vulpix* - Needs a stone to reach its full potential, and it has a limited movepool.
Zubat - By the time you realize Zubat is bad you'll have wasted your time killing all of them in caves.
Paras - It's rare, weak, and does nothing.
Venonat - Decent stats and movepool, but it's outclassed.
Growlithe* - It's weak with a shallow movepool, and it's obtained late.
Machop - Too hard to get it to full potential, and it's annoying to train.
Tentacool - See Zubat.
Ponyta - It has a poor movepool despite its good stats.
Magnemite - It needs TMs to reach its full potential and has limited options.
Seel - It's obtained late and is weak with a bad movepool.
Grimer - By the time you can obtain one there are better options.
Shellder - Its stats are mediocre, despite its okay movepool.
Onix - There are better options.
Krabby - It has decent stats, despite a poor movepool.
Voltorb - It has good Speed and okay power and movepool, but there are better options.
Cubone - It's hard to obtain and level with almost no reward.
Hitmonlee - It's easy to get, with a poor movepool.
Hitmonchan - See above.
Lickitung - Obtained late with slow EXP gain in spite of its good movepool.
Koffing - Obtained late, and it needs TMs to be effective.
Chansey - It has good bulk, but it's extremely rare
Tangela - It's generally bad, outclassed at nearly everything.
Kangaskhan - It's hard to find, and one attacking type isn't fun.
Horsea - It's Rare-ish with lackluster stats and a forgettable movepool.
Goldeen - Decent power, but it has a poor movepool.
Scyther - Obtained very late, despite it being decent.
Electabuzz - Poor movepool and stats prevent it from being good.
Magmar - It's obtained late, and despite its good power it needs TMs to reach its full potential.
Pinsir - Bad movepool and stats, and it's inferior to Scyther.
Tauros - Hard to obtain, poor movepool, despite its decent power and Speed.
Ditto - It's Ditto...
Flareon - Its has a bad movepool and low Speed, despite its great Attack.
Porygon - Does nothing worth mentioning, and it's obtained too late to be useful.
Omanyte - Hard to obtain, decent power-wise, but its bad movepool holds it back.
Kabuto - See Omanyte.
Aerodactyl - Good stats, okay movepool, but it's annoying to train by the time you get it.
Moltres - It's caught late and has a poor movepool.
Dratini - Caught way too late to prove effective and has a poor movepool.
Yellow
Changes from RB:
Bulbasaur High -> Mid
Mankey Mid -> High
Farfetch'd Mid -> Low
Meowth Mid -> N/A
Jynx Mid -> N/A
Weedle Low -> N/A
Ekans Low -> N/A
Koffing Low -> N/A
Electabuzz Low -> N/A
Magmar Low -> NA
High
Charmander - It's obtainable relatively quickly, and has pretty decent stats.
Squirtle - It's obtainable early on and has a great movepool.
Spearow - It's quick to level, decent stats, and it can learn Fly.
Pikachu - Bad early on, but it makes up for it later with type coverage.
NidoranF - It has great type coverage when fully evolved, and can be caught early on.
NidoranM - Slower than the Female, but it's a bit stronger and has good coverage.
Diglett (+Dugtrio) - It's very fast, has decent power, and it's easy to find.
Mankey - It can be obtained extremely quickly, and is very helpful for the first few gyms.
Abra - It's hard to obtain, but it's extremely fast and powerful with good coverage.
Geodude - Extremely easy to obtain, and it has very good power later in the game.
Doduo - Fast and moderately powerful, and it's easy to level up.
Staryu - Very fast and it has good power and great movepool, it's also easy to train.
Mr. Mime - It's hard to find, but it has a very good movepool if it's caught early.
Snorlax - Obtained later in the game, but it's extremely powerful, despite being hard to catch.
Zapdos - It has great stats, a good movepool, even though it's hard to catch.
Mid
Bulbasaur - It's obtained a little later than other starters, and its movepool isn't brilliant.
Caterpie - It evolves early, but lacks power.
Rattata - Obtained easily, but it has a poor movepool.
Sandshrew - It doesn't have a great movepool or stats.
Clefairy - Very hard to find, and it's difficult to level.
Jigglypuff - Hard to train, and it doesn't have much of a movepool.
Oddish - Decent movepool, but its type coverage isn't great.
Psyduck - Difficult to find, and its movepool is let down by its stats.
Poliwag - Easy to find, but it's also hard to train and doesn't have much of a movepool.
Bellsprout - Its stats aren't great, and it gains exp slowly.
Slowpoke - Decent typing, but it has poor stats and movepool.
Gastly - Fast and powerful, but it's hard to obtain.
Drowzee - Good movepool, but it's slow to level.
Exeggcute - It has good typing, movepool, and stats, but it's obtained very late.
Rhyhorn - Very good Attack, despite it being slow to level and obtained late in the game.
Magikarp - Very difficult to level, and Gyarados is subpar in Yellow.
Lapras - It's found at too low of a level for the stage the game is at.
Vaporeon - Good stats, despite being hard to obtain.
Jolteon - Very good stats, but it's hard to obtain.
Articuno - It's difficult to obtain, and its movepool isn't great.
Low
Pidgey - It's weak, slow, and extremely common.
Vulpix - Small movepool, and it's weak and difficult to level.
Zubat - It has bad typing, and is very weak despite being fast.
Paras - Hard to find and level, and it's extremely slow.
Venonat - Hard to find, decent movepool, not worth the effort of leveling
Growlithe - Hard to obtain, and it has subpar stats and movepool.
Machop - Easy to obtain, but its movepool lacks coverage and it's slow.
Tentacool - It's extremely common, and is weak with poor coverage.
Ponyta - It has poor stats, and is obtained late in the game.
Magnemite - It has a bad movepool, and it's hard to level.
Farfetch'd - It's difficult to obtain, and not worth the trade since it can't evolve.
Seel - It's obtained very late, and has poor coverage.
Grimer - It's easy to find, but has poor stats and movepool.
Shellder - It has poor stats, movepool, and typing.
Onix - Easily obtained, but it's very weak later on.
Krabby - Poor stats and it's hard to get, despite having a good movepool.
Voltorb - It's hard to level and has a a poor movepool, despite having good Speed.
Cubone - It's weak and obtained late, with a bad movepool.
Hitmonlee - It's obtained relatively late and at a very low level.
Hitmonchan - It's Hitmonlee with worse stats.
Lickitung - Very hard to find, and it has a bad movepool.
Chansey - Extremely annoying to obtain, and it's very weak.
Tangela - It's hard to find, and obtained at low level with poor stats.
Kangaskhan - It's hard to find, has a bad movepool, and is difficult to level.
Horsea - It's difficult to level, has low stats, and a shallow movepool.
Goldeen - Its movepool is poor, despite its decent stats.
Scyther - It's extremely hard to find, and its movepool is bad despite its stats.
Pinsir - It's hard to find and is worse than Scyther.
Tauros - It's extremely hard to find, and is obtained too late to be effective.
Ditto - It's Ditto...
Flareon - Bad stats and movepool, and it's difficult to obtain.
Porygon - It doesn't evolve, has poor stats, and is obtained at an extremely low level.
Omanyte - It's obtained too late and at too low a level to be useful.
Kabuto - Omanyte with worse stats.
Aerodactyl - Omanyte with a better movepool.
Moltres - Obtained way too late, and it has bad typing and movepool.
Dratini - Extremely hard to obtain and level, and its movepool is very small.
Not tiered (These should be uniform, so either N/A or Not tiered.)
Weedle
Meowth
Ekans
Jynx
Koffing
Electabuzz
Magmar
Mewtwo
Mew
Gold/Silver
High
Chikorita - It's a starter, and it has a good movepool.
Cyndaquil - It's a starter, and it has very good stats
Totodile - It's a starter, and is easy to train with good stats later in the game.
Spearow - Easy to obtain, and it has very good stats.
Rattata - It's easy to obtain, and has a decent movepool.
Mareep - Great movepool and stats, and it's obtainable fairly early.
Wooper - It has good stats, and is easy to train.
Gyarados [Event] - It's difficult to catch, and is caught at a low-ish level, but it has a good movepool and stats.
Drowzee - It has a good movepool, and is easy to obtain.
Abra - It's difficult to obtain, but has an extremely good movepool and stats.
Sudowoodo - It's obtainable early on, and it has decent stats.
Machop - It's easy to level, and has good stats.
Eevee (Espeon) - It has very good stats, it's obtainable early on, and is easy to level.
Ho-oh [Gold] - It's obtained late, but it's extremely powerful.
Lugia [Silver] - Same as Ho-Oh.
Mid
Pidgey - It's easy to get, but it's not as strong as Spearow.
Hoothoot - It has a better movepool than Spearow, but worse stats.
Sentret - It's easy to get, but it has poor stats.
Caterpie - It evolves very fast, but has a poor movepool.
Geodude - It has good stats, but it's hard to level later on.
Jigglypuff - It has bad stats and movepool, despite being easy to get.
Sandshrew - It has poor stats, despite a decent movepool.
Gastly - It has very good stats, but is difficult to level early on.
Bellsprout - It's easy to find, but it has poor stats.
Poliwag - It has decent stats, but it's hard to level.
Magikarp - It's easy to find, but is extremely hard to level despite being decent later in the game.
Slowpoke - It's easy to find and has moderate stats, but it's hard to level.
Oddish - It has poor stats and movepool, but its easy to train.
NidoranF - It's too average to be of any use.
NidoranM - It's slightly better than the Female, but still not great.
Snubbull - It has average stats and movepool.
Mankey - Slightly hard to obtain, despite it having decent stats and movepool.
Miltank - Hard to obtain, but it has good stats and movepool.
Magmar - Obtained a little late, and it has bad stats despite a good movepool.
Jynx - It's obtained very late, but it has a good movepool and decent stats
Tentacool - It's extremely easy to find, but is often low leveled and difficult to train.
Chinchou - It's hard to find, but it has good stats, movepool, and typing.
Doduo - It's hard to find despite its decent stats.
Lapras - Very hard to obtain, but it has decent stats.
Snorlax - It's hard to obtain, but has good stats.
Suicune - It's very hard to obtain, but has very good stats and movepool.
Ho-oh [Silver] - Obtained extremely late, but it is still the most powerful (the most powerful what?)
Lugia [Gold] - See above.
Low
Pikachu - It's hard to get, and it has a poor movepool.
Weedle - It evolves early, but has bad stats and movepool.
Ledyba - Its stats are poor and it's difficult to level.
Spinarak - It has poor stats and movepool.
Zubat - Fast and common, but it's weak and has a bad movepool.
Clefairy - It's extremely hard to get, and isn't worth the effort.
Togepi - Its egg hatches too late, and its stats are poor.
Ekans - Its stats aren't great, and its movepool is worse.
Dunsparce - It has horrible stats and is difficult to train.
Unown - It's absolutely terrible in all aspects.
Onix - It's weak, hard to evolve, and has a poor movepool.
Hoppip - It's very weak and hard to train.
Paras - It's slow, has a poor movepool, and is difficult to train.
Goldeen - Weak, poor movepool, and it's outclassed by others.
Ditto - It's Ditto...
Pineco - It's weak and has a poor movepool.
Yanma - It's very weak and hard to obtain
Sunkern - It's extremely weak and nearly impossible to train.
Exeggcute - It's found late, and is hard to catch too.
Wobbuffet - It's hard to obtain and has a rubbish movepool.
Venonat - It's weak and isn't worth training.
----------
Scyther - Hard to obtain and evolve, decent stats, poor movepool
Pinsir - Is a worse Scyther
Heracross - Slow, poor movepool, hard to obtain
Koffing - Weak, hard to train
Grimer - Obtained late, poor stats and movepool
Magnemite - Obtained late, decent stats, poor movepool
Voltorb - Weak, poor movepool, hard to find
Aipom - Hard to obtain, poor stats
Vulpix - Hard to obtain, poor movepool
Growlithe - Poor stats and movepool, not worth training
Stantler - Weak, obtained late
Marill - Weak, bad movepool, hard to train
Diglett - Weak, poor movepool, hard to obtain
Meowth - Weak but fast, obtained late, difficult to train
Psyduck - Hard to obtain, difficult to train, poor movepool early on
Tyrogue - Very difficult to obtain, annoying to evolve into the correct form
Girafarig - Very difficult to obtain, poor stats
Tauros - Obtained late, poor movepool
Electabuzz - Obtained very late, poor stats
Mr. Mime - Obtained very late, good movepool but dismal stats
Smeargle - Obtained extremely late, stats aren't great, hard to get the moves you want
Farfetch'd - Difficult to obtain, outclassed by most other Flying-types
Natu - Weak, obtained very late
Qwilfish - Very poor stats and movepool
Krabby - Movepool is bad, slow, hard to find
Shuckle - Slow, horrible attack and movepool, not worth using
Staryu - Extremely powerful, difficult to evolve
Shellder - Obtained late, weak with a bad movepool
Corsola - Difficult to obtain, poor stats
Remoraid - Difficult to obtain and train
Seel - See Shellder
Lickitung - Obtained too late to be useful, poor stats
Tangela - See Lickitung
Eevee (Jolteon) - Difficult to obtain, poor movepool, good stats
Eevee (Vaporeon) - Difficult to obtain, movepool is poor and stats are subpar
Eevee (Flareon) - Difficult to obtain, movepool and stats are poor
Eevee (Umbreon) - Outclassed by Espeon, movepool still isn't great
Horsea - Hard to find and train, movepool is poor
Gligar - Stats are poor, obtained at a low level
Delibird - Weak, poor movepool, obtained too late
Swinub - Hard to train, poor movepool
Teddiursa - Hard to train, slow, poor movepool
Phanpy - Obtained late, poor movepool
Mantine - Weak, bad movepool, hard to catch
Skarmory - Slow, weak, poor movepool
Ponyta - Obtained late, very poor in all regards
Cubone - Weak, obtained very late
Kangaskhan - Obtained extremely late and hard to train
Rhyhorn - See Kangashkan
Murkrow - Weak, poor movepool
Slugma - Very weak and slow, bad typing
Sneasel - Very hard to find, weak
Misdreavus - Extremely hard to find, low stats
Porygon - Very difficult to obtain, poor stats
Chansey - Very difficult to obtain and train
Aerodactyl - Obtained extremely late
Raikou - Too much effort required
Entei - See above
Dratini - Obtained too late, extremely hard to train
Larvitar - See Dratini
N/A
Kabuto
Omanyte
Bulbasaur
Charmander
Squirtle
Articuno
Zapdos
Moltres
Mewtwo
Mew
Celebi
Crystal
Crystal changes:
Poliwag: Mid -> High (obtainable much much earlier)
Suicune: Mid- > High (event now)
Staryu: Low -> Mid (Water Stone available much earlier)
Exeggcute: Low -> Mid (Leaf Stone available much earlier)
Growlithe: Low -> High (available much earlier AND Firestone available much earlier)
Eevee (Vaporeon): Low -> Mid (Water Stone available much earlier + Surf HM, other Eeveelutions don't have sufficient movepools to become better)
Ho-oh: to Low, since you need to hunt down Raikou and Entei AND do the sidequest only to obtain it post-Elite Four
Lugia: same as Gold Lugia, AKA Mid
And some Pokemon are unavailable in Crystal.
High
Chikorita - Starter, good movepool
Cyndaquil - Starter, good stats, good typing
Totodile - Starter, decent stats and movepool
Spearow - Easy to obtain, easy to train, decent power
Rattata - Easy to obtain, good movepool
Poliwag - Relatively easy to obtain, great stats later on
Wooper - Easy to train, great typing
Gyarados [Event] - Obtained late, good power and movepool
Drowzee - Obtained relatively early, decent movepool
Growlithe - Easy to evolve, decent stats
Abra - Hard to obtain, very good stats and movepool
Sudowoodo - Obtained early, decent stats
Machop - Easy to train, good stats and movepool
Eevee (Espeon) - Great stats and movepool, obtained early
Suicune - Guaranteed encounter, great stats
Mid
Pidgey - Obtainable early, weak later on
Hoothoot - Good movepool, weak and difficult to obtain (time restraints)
Sentret - Easy to obtain, very weak
Caterpie - Evolves fast, weak in the later stages of the game
Geodude - Decent stats, difficult to train
Jigglypuff - Easy to obtain, decent movepool but poor stats
Sandshrew - Somewhat hard to obtain, poor movepool
Gastly - Obtained early on with a good movepool and stats, hard to train
Bellsprout - Easy to obtain with a decent movepool, poor stats
Magikarp - Hard to train, good stats once it evolves
Slowpoke - Easy to catch, difficult to train but good stats
Oddish - Easy to catch, weak and hard to train
Exeggcute - Obtained late, good typing and stats
NidoranF - Easy to obtain, but stats aren't the best and needs TMs to reach full potential
NidoranM - Slightly better stats than NidoranF
Snubbull - Weak later on, easy to train
Mankey - Easy to train and obtain, weak in the later stages of the game
Miltank - Obtained late, no real power
Magmar - Relatively easy to obtain, poor movepool
Jynx - Obtained very late, decent movepool
Tentacool - Easy to obtain, poor movepool
Staryu - Obtained somewhat late, good stats and movepool
Chinchou - Hard to get, good typing and movepool
Doduo - Difficult to train and has worse stats than other birds
Eevee (Vaporeon) - Obtained early, poor movepool
Lapras - Difficult to obtain, low leveled
Snorlax - Obtained late, very hard to train
Lugia - Obtained extremely late, very powerful
Low
Pikachu - Difficult to obtain, poor movepool
Weedle - Evolves fast, terrible stats
Ledyba - Poor stats and typing
Spinarak - Difficult to train, weak in the later stages of the game
Zubat - Easy to obtain, difficult to train
Clefairy - Very rare, not worth the effort
Togepi - Egg hatched at a low level, poor stats
Ekans - Easy to obtain, poor stats and movepool
Dunsparce - Extremely weak
Unown - Horrible stats and movepool
Onix - Weak in the later stages of the game, difficult to evolve
Hoppip - Extremely weak, poor movepool
Paras - Very weak and hard to train
Goldeen - Hard to train, stats are poor
Ditto - It's Ditto...
Pineco - Poor stats and movepool, hard to find
Yanma - Hard to obtain, weak in the later stages of the game
Sunkern - Extremely hard to train, bad stats
Wobbuffet - Poor movepool and stats
Venonat - Hard to train, poor typing and stats
Scyther - Difficult to obtain, movepool isn't great, isn't that powerful
Pinsir - Weaker Scyther
Heracross - Rare, poor movepool
Koffing - Easy to obtain, difficult to train
Grimer - Poor stats and movepool
Magnemite - Obtained late, bad typing and stats
Voltorb - Difficult to train, obtained late
Aipom - Rare, very low stats
Stantler - Weak and difficult to train, has a decent movepool
Marill - Rare and difficult to train, poor stats
Diglett - Decent stats, poor movepool and hard to obtain
Meowth - Obtained relatively late, poor movepool
Psyduck - Difficult to train, poor stats and is weak in the later stages of the game
Tyrogue - Extremely hard to obtain, difficult to evolve correctly
Tauros - Obtained late, poor movepool
Electabuzz - Obtained very late, poor movepool
Mr. Mime - Extremely hard to obtain
Smeargle - Very hard to find, difficult to get good movepool
Farfetch'd - Hard to find, poor stats
Natu - Extremely hard to find, poor movepool and stats
Qwilfish - Very poor movepool and stats
Krabby - Obtained late, often low-levelled
Shuckle - Extremely weak, horrible movepool, and very, very, rare
Shellder - Obtained late, poor stats
Corsola - Rare, poor movepool
Seel - See Shellder
Lickitung - Difficult to obtain, poor stats
Tangela - Obtained late, poor stats and movepool
Eevee (Jolteon) - Very good stats, but poor movepool and difficult to evolve
Eevee (Flareon) - Worse than Jolteon
Eevee (Umbreon) - Decent stats, horrible movepool
Horsea - Hard to obtain, poor stats and movepool until final evolution
Gligar - Rare, obtained late, very poor stats
Delibird - Obtained very late, poor stats and typing, worse movepool
Swinub - Obtained very late, difficult to train, poor stats
Teddiursa - Poor stats and movepool, difficult to train
Phanpy - Decent stats, but poor movepool without TMs or breeding
Mantine - Poor stats and movepool, difficult to obtain
Skarmory - Hard to obtain, poor stats
Ponyta - Very poor stats and movepool
Cubone - Difficult to obtain and train, poor stats
Kangaskhan - Obtained very late, poor movepool
Rhyhorn - Difficult to find and train, has poor stats and movepool
Murkrow - Hard to obtain, poor stats
Slugma - Obtained late, poor stats and movepool
Sneasel - Very rare, poor movepool
Misdreavus - Obtained extremely late, poor movepool
Porygon - Very hard to obtain, poor stats
Chansey - Obtained late, poor stats, difficult to train
Aerodactyl - Extremely hard to obtain, poor movepool without TMs
Raikou - Extremely hard to find and catch
Entei - See Raikou
Dratini - Obtained very late with a very low level, hard to train
Larvitar - Obtained extremely late, very low level, very hard to train
Ho-oh - So difficult to obtain it is not worth it
N/A
Mareep
Vulpix
Girafarig
Remoraid
Kabuto
Omanyte
Bulbasaur
Charmander
Squirtle
Articuno
Zapdos
Moltres
Mewtwo
Mew
Celebi
