Bulbasaur! :D He’s my favorite grass-type AND my favorite starter of all time!
Everyone always chose Charmander or Squirtle when I was younger, but I always felt Bulbasaur was the best choice, especially considering the first 2 gyms are weak to grass. Hell, even the 3rd one was pretty weak against grass.
Aside from that fact, Bulbasaur is just adorable & awesome in every way. :)