When playing R/B/G or FR/LG, I almost always go with Bulbasaur.
1.Bulbasaur: It has a very good typing and can take down Gyms 1-4 in Kanto with ease. Plus, it has solid stats and I just love my Bulbasaur 8-3
2.Charamander: Charamander's my second choice because it struggles early on, with so many Water-type and Rock/Ground-Type trainers between Pewter City and Vermillion. However, it's probably the best Fire-Type in-game other than Moltres and maybe Magmar. And, I wuv Charizard, lol.
3.Squirtle: Squirtle comes as my third choice because early on, it has a harder time than Charamander due to the second, thrid, and fourth gyms being Water-, Electric-, and Grass-typing respectively. Also, there are better Water-types like Gyrados and Lapras (FTW). But, if you want novelty, than its okay. But I do love my Balstoise.