Out of the classic 8 staple Pokemon of RBY OU, it's 3 Normal, 3 Psychic, and 2 that are neither; if you include all the niche 'mons, you add Jynx and Slowbro on the Psychic side and maaaaybe Persian on the Normal side.
And, as you've had pointed out to you, "Psychic's bad because it's banned" ain't the greatest argument.
i dont think he's saying "psychic is bad because it's banned" i think he is saying "mewtwo and mew are not OU pokemon and so they are not the best pokemon in rby OU" maybe if we were discussing the rby uber metagame it would be a different story. there's a distinction between metagames and generations here that i'm sure you are simply forgetting.
Salamence sounds like a better fit than Dragonite in my opinion, it only existed through the last two gens but it was incredibly overpowered in DPP and had more tools to work with on ADV. Nite was barely useful on RBY and GSC so that doesn't exactly speak a lot about dominance.
Then we run into the same issue as with GSC Celebi. It seems that the consensus here is that Celebi's existence in OU should be disregarded for the most part. Following the same logic, I don't think Salamence deserves anything here for only one gen.
if we're only considering adv and dpp celebi then i'm not sure celebi should be in the discussion at all (which somehow feels so much more wrong than disregarding something like jirachi). so stuff like blissey vap drag egg raikou forry whatever
This is true in RBY OU solely because the best Psychic-types - the two bulky Psychics with Recover - were the original Uber tier. Moreover, the Normal-type that stops most Psychic-types - Chansey - has utterly no use of its STAB and would be strictly better were it Psychic. For that matter, literally every single-typed Pokemon in RBY would be strictly better were it dual-typed with Psychic. The same is not true of Normal.
Every single-typed Pokémon in RBY would be strictly better were it dual-typed with Ghost, too. And some Pokémon would have more to gain from Normal-typing than from Psychic-typing.
But you can't mix and match your different kinds of arguments. Either you look at the OU metagame as it is--led by three Normals--or you look at types on their own merits--comparing the value of Normal STAB vs. Psychic STAB + resistance vs. Normal immunity vs. Ice STAB + resistance + immunity to freeze, etc. The moment you try to take on both tacks, your argument becomes incoherent.
Where is cloyster? It definitely deserves a spot for 3 generations of being OU, and being pretty good in all of them. Heatran too maybe, I know it was only around for one generation, but heatran is the face of gen 4 OU.
Just to throw in a new wrinkle, if we give any relevance to the 3rd Gen "200" meta, before the FR/LG release, it gives a huge boost to Alakazam's case as perhaps #10 on the list, since he was a defining pokemon in that meta, in addition to being one of the biggest threats in RBY.
Unfortunately, he's not really a factor in either GSC or DPP, so he might be muscled out by other mons who were forces in two gens (Exeggutor, Jirachi, Salamence if his run in DPP OU counts).
I don't think a clear RBY ubers metagame ever existed for Mewtwo to dominate. It's more of a theoretical thing.
I remember back on the PBS before "metagame" (as in ubers, OU, UU, etc.) became a well-trod subject. Most people had an understanding that you wouldn't bring Mew or Mewtwo into the battle but you'd fight the occasional random who didn't know better. Also the simulator freely let you put illegal moves on your Pokémon; I fondly remember being Spored by my little sister's lead Tauros.
Mewtwo owned the RBY metagame, he was not too popular on the early simulators, but he was almost always used on Stadium and Link Battles (at least the ones I had, and I heard), Slowbro's Tobybro set was created specially with the intention of counter the spam of Mewtwos, and he still owned on GSC a lot (Celebi and Lugia did more, anyway), the reason why he wasn't used on simulators was because the RBY metagame was almost just played in-live, as the simulators start was a bit... obscure, and it was more competitive and a trully way to battle more for the end time of GSC.
Anyway, I think we're talking more about OU (OverUsed) than Ubers, as Ubers were more banned than not from GSC and nexties generations, and this's about the Most Dominant Pokémon in History, in order words, more than a just single generation. If ubers were available to being put on the rank, then Kyogre should be #1, Kyogre shapped the ubers-metagame a lot more than even Snorlax with the OU second generation.
About the place #7, I could rather nominate Chansey/Blissey or Suicune, Chansey was a must on RBY (a team of 6 Chansey even winned the first official japanese tourney), Blissey was maybe not the best Pokémon, but was an excelent option for some roles on OU, and was used a lot (maybe a bit more than deserved, but still), on ADV it's not even need to say how common and fearsome was the SkarmBliss core, and Blissey was still a top threat on DPPt (even if Chansey and Blissey are not take care as a single Pokémon, Blissey should still be on the Top 10). Suicune by other hand is the same definition of bulkyphazer that can check almost any offensive Pokémon on the game, Suicune + Raikou were an almost flawless core on GSC, on ADV, Suicune was maybe one of most dominant Pokémon ever with Calm Mind, and was still a top threat on DPPt.
While Heatran may be the poster boy of the post-Dragons DPP era, one generation of dominance doesn't give it a spot on a list of the most dominant mons in the history of the game. Not to mention that while Tran's one of the best mons in the metagame (I'd make a case for Tyranitar being better tbh), it definitely is not "dominating" the same way Tauros was in RBY, Snorlax was in GSC, or Tyranitar/Celebi were in ADV.
I think Mewtwo has more hard counters in RBY ubers than Snorlax in GSC OU. You're using between 2-4 pokemon to counter either in both cases, but Mewtwo is just more predictable than Snorlax. It's going to have Amnesia, Rest/Recover, and Psychic. It only has one toss up move, which it needs to counter slowbro (tbolt), other mewtwo (ib), or random exploding shit (barrier) and other random stuff (toxic is decent). And it can't do all of it. And there's still Chansey and Mew. Mewtwo in ubers is just a luckfest both to see who freezes first or CHes at opportune times or whatever, and whether or not your 4th move pays off. That doesn't stop Mewtwo from being far and away the best pokemon in RBY, but that doesn't speak volumes at all in a face off against GSC lax. Either way, ubers RBY is a terrible metagame.
if Skarmory made it on the list, so should Blissey IMO. I've started in gen 4, and blissey was one of the sole reasons that special attackers had to had a way to beat her if they wanted to be OU: i.e. Blissey alone managed to hold off a good number of viable special attackers in gen 4 (and most likely previous gens bar 1) who simply couldn't beat her. Not to mention that Gen 4 became the rise of the offense, meaning that in Gen 2 and 3 stall/defensive were the way the go: i.e. Blissey was made even more viable methinks. Also, the Blissey-Skarmory combo deserves to be mentioned.
Nah, Chansey x Blissey is Position 5-7#, probably 5#, but Blissey alone is 7-10#, I could rather say that she is number 8# or 9# basically because on GSC, she was a bit useless, not need to have her with Raikou and Suicune walling the entire metagame and doing more than here on each turn, and she had competition for the role of Heal Beller, too.
ADV's time were the best Blissey's time, but even then, she was not so-dominant as Skarmory, and basically the same goes with DPP, but she was important enough to form part of this Top 10, anyway.