If you are talking about pokemon R/B/Y, then Bulbasaur wins for the fact that he becomes Venusaur. To anyone ignorant of this fact, any pokemon that uses a high critical hit ratio move and has a base speed of at least 60 something will ALWAYS get a critical with said move. So Venusaur not only gets STAB razor leaf, but an always critical hit, not mentioning the fact that he has a plethora of status inflicting moves on his side.
He still isn't that bad in-game when fighting trainers.
Squirtle, I never really liked him. He never had much use except for walling, and other water pokemon like Lapras could do a much better job at that AND handing out a few blows as well.
Charizard was good for a while, but he absolutely fell to the bottom when Stealth Rock was introduced in Wi-fi battles. That means he already has a 50% health handicap when switching in, and it especially sucks that the best choice(and possibly only good one) is bellyzard. That isn't mentioning how common moves like Surf and Rock Slide are, but I'll ignore that.
Well, that's my two cents on this subject.
