Pidove is just a rip-off of the Pidgey/Taillow/Starly lines.
Purrloin = Poochyena
Patrat = Rattata/Sentret/Zigzagoon/Bidoof
Purrloin = Poochyena?
This one is like they didn't even try...
But overall, some early-route birds, bugs and rodents are to be expected. Birds, bugs and rodents are quite "basic" creatures, and a great way to introduce the concept of Pokémon. Meanwhile, veteran players crave to see new Pokémon at the start of the game, to underline that this is, indeed, a
new Pokémon generation. With that in mind, it's understandable that GameFreak keep making similar designs for the start of the dex.
What is unforgivable in Gen. V, though, is that they kept churning out new Pokémon built to near-identical specifications to the old ones, making half the line. For instance:
Munna line = Drowzee line (Sleep-related Psychic Pokémon with a tapir-related design)
Roggenrola line = Geodude line (Three-stage, ubiquitous Rock type family, final evolution by trade)
Woobat/Swoobat = Zubat/Golbat (Goddamn bats troubling you through every step of a cave)
Drilbur line = Sandshrew line (Bipedal, Ground type moles)
Audino = Chansey (Pink blob with defensively-oriented stats, a high Exp. yield, and a likeness to nurses)
Timburr line = Machop line (Humanoid mono-Fighting types, final evolution by trade)
Tympole line = Poliwag line (Blue, Water type tadpoles evolving into frogs)
Throh/Sawk = Hitmonchan/Hitmonlee (Humanoid, clothed mono-Fighting types inspired by martial arts)
Cottonee line = Hoppip line (note that their later Fairy typing fixed this)
Lilligant = Bellossom
Crustle = Parasect (relatively small bug underneath massive shell which is not really part of its body)
Cubchoo line = Teddiursa line (cuddly small bear evolving into ferocious, bipedal bear)
Bouffalant = Tauros (big, bull-like Normal Pokémon)
Emolga = Every Pika-clone ever.
Rufflet line = Spearow line (Normal/Flying birds with a somewhat ferocious nature. The pre-evolution has a fuzzy, feathery head, while the evolution soars on great wings)
Also, Galvantula's official art has it in the exact same pose as Ariados. The design is original in itself, but at first glance, it looks like another copy.
However, apart from these glaring design repetitions, most of Gen. V is actually pretty well designed. Okay, some of the designs are ugly, but at least they are original. It seems pretty clear that the designers wanted certain "roles" to be filled by Pokémon in the games, just as old Pokémon had filled them previously, and they designed new ones to replace the old ones which used to do the exact same job. However, once the obligatory role list was filled, they let themselves loose with creative designs for the rest of the dex.