I don't choose by element. I don't know why I choose the ones I choose. I picked Grass in Gen I, Fire in Gen II, Fire in Gen III, and Water in Gen IV. I guess I pick primarily based on aesthetics. (Though I suppose it's possible that I knew that in Gen I that Squirtle was supposedly like Easy Mode, Bulbasaur was Normal Mode, and Charmander was Hard More, and I do think I knew what the final evolutionary forms looked like in Gen IV at the very least, which I believe influenced my decision slightly.)
I don't choose by element any more (so I voted that), but when I first started playing Pokemon I would choose grass-type starters. So I went with Bulbasaur and Chikorita in Blue and Silver respectively.
Actually, Bulbasaur is Easy Mode, and Squirtle is Normal Mode.
Bulbasaur has an advantage over every gym leader until like, the 4th or 5th city. Squirtle basically only has an advantage over the first gym, and after that he's either "even" with the gym type (Misty's Water-Types) or at a supreme disadvantage (Lt. Surge's Electric-Type).
I'm allover the map. When I first played Red version (via emulator) I picked Bulbasaur purely for the early advantage Grant mentioned above. When I got my own Gameboy and Blue Version though, I went with Squirtle- Because every one of my friends went with the cool fire lizard and I wanted to kick their ass . But I've grown to love Squirtle in his own right. Turtles kick ass.
Other than that I seem to go by visual aesthetics, so I'm all over the map. Cyndaquil in Gen II, Torchic in Gen III, Turtwig in Gen IV and Oshawott in Gen V
Water can take out a lot of pokemon. Most water starters focus on defense and is usually slow. Swampert has to be my favorite water-starter because of it's immunity to electric attacks. Plus, he hits hard!!!
I'll be glad when they switch up the starters to Psychic, Dark, Fighting. Or incorporate it unto the regular starters so that everybody has a chance in beating each other. (Water-Psychic, Fire-Dark and Grass-Fighting). If I see one more Fire-Fighting starter Pokemon, I'm gonna go ape shit.
Yeah, he's good against Blaine but by that part of the game, you're going to have a full stable full of awesome monsters to destroy Blaine with!
Also, Squirtle is automatically better than Charmander simply because of the final evolutions for both. Charmander basically turns into a generic-looking, cartoony fire-breathing dragon. If I didn't know any better, I would have guessed Charizard would be a high school mascot or something.
Blastoise on the other hand, is a giant, bipedal war tortoise with twin cannons sticking out of his shell. He's far more unique and creative than the derivative fire newt with wings.
I usually pick fire. It's got it's weaknesses and such, but most of them have enough offensive and speed status to make it up for those.
But regardless of tactics and knowledge in the series, as a kid, I always picked the fire starter. The only generation I chose the water type was gen II. I didn't like Cyndaquil very much and Totodile looked awesome. I just love alligators, crocodiles and such.
Come to think of it, Gen II starters weren't that good, as in technical stuff. Even in weather teams, I rather get other pokémon to do the job.
Also, I haven't played through Gen V yet, although I do know it's share of pokémon well enough. I don't think I'd like to get a Tepig for some fair amount of reasons, so I would get the water starter as well.
Bulbasaur has an advantage over every gym leader until like, the 4th or 5th city.
Are you sure about that? From what I recall, he doesn't even learn any decent grass type moves until you're about to the 2nd or 3rd city, but Squirtle learns decent water moves before you get to the 1st city, making the battle with Brock much easier if you have a Squirtle than a Bulbasaur. Granted, you're right that Squirtle doesn't have an advantage over Misty, while Bulbasaur should, but I don't think Grass/Poison has any advantage over Electric. (Just looked it up; Grass has no advantage over Electric, but Electric does have a disadvantage over Electric.) And then the 4th city is Grass, if I recall correctly.
So you might could make the argument either way since picking Squirtle is way easier in the beginning, but Bulbasaur could be easier in the long run (assuming you stick with your starter throughout the game; though really, since we're excluding Brock for Bulbasaur since it doesn't have any good Grass moves at that time, that still gives Bulbasaur and Squirtle two gyms apiece where they do particularly better than the other starters).
EDIT: Just looked up Bulbasaur's move list. Looks like he learns Vine Whip at Level 9, which is an okay Grass move that you might get before getting to Brock, so he's back on the fence again...
Yeah, Bulbasaur learns Vine Whip pretty early on, so he's super-powerful against Brock's rock-type monsters, and super-powerful against Misty's water-types. Bulbasaur doesn't have an advantage over Lt. Surge's electric-types, but the electric-type moves are "not very effective" against grass-type. Erika's grass-type monsters are on par with Bulbasaur, so he's kind of on a level playing ground at that point. Though by then, you should have a pretty powerful flying-type (like a Pigeotto or something) to take out Erika's gang.
Bulbasaur is really only weak against Sabrina's psychic-type, Blaine's fire-type, and Koga's poison-types. But you get to those gyms so late in the game it's kind of moot point.
And of course Bulbasaur is at a huge advantage again against Giovonni's ground-types.