I started with Pokemon Blue (ahhh, the good ol' days), and my first Pokemon was Bulbasaur because even when I was a naive 11 year old, I was still a fan of cold, hard logic. Bulbasaur is strong against both rock and water types - oh, and what kind of types do the first two gym leaders use? What's that? ROCK and WATER types, you say? By jove, I best be picking Bulbasaur!
I never picked Charmander - sure, the whole "fire dragon" thing is cool, but he is just so useless early game; by the time that he actually becomes useful against the gym leaders, there's absoloutely no reason why you can't have a well-balanced team which is effective against any type of Pokemon. Plus, Venasauar was awesome - he was like some sort of enormous Plant Beast which shot lasers; that's fucking cool.
In gold, however, I went with Cyndaquil, because Cyndaquil kicks ass.