I usually go with fire unless one of the others has a cooler evolution and/or I want to mix things up.
I always pick the water starters first, since my brother almost always picks fire (unless there is a cooler evolution he likes). Call it sibling rivalry.
I choose whichever starter that I like the designs of their base form and final evolution of most, regardless of typing.
I usually play knockoffs (I don't have a 3DS unfortunately) so I always go with Torchic, my favorite starter. But generally I choose the Pokémon whose evolutions I like design-wise, so my starter choices will often seriously vary.
I sold my soul to the Fire starters, I MUST always chose a fire starter at the first playthough of every Pokémon game (sans spinoffs) or things will go horribly wrong. (Pearl had Piplup, and my game got glitched to no return when I did void hops and let my cousin test some AR codes on it. FireRed had Venusaur and I was stuck for over a year at the elite four/champion, ect)
I like the Water starters. Popplio, Totodile, ect. I just find them very cute creatures that turn into RAGING BEHEMOTHS OF COMPLETE AND UTTER DESTRUCTION-I mean, they certainly help in the journey. #MissingNo
I started in bluw with water andd since gen 2 always fire. Bht I like all 3 starters of gen 2. I hardly use grass . Sometjmes water but mosrly fire. However in sm I choose grass as I didnt like the final evo of the fire starter
I dont know why, but I always went for the water starters. There was never any good reason, I just never liked fire starters.
Usually based on designs in each of its evolution. Most of the time I'll either choose grass or fire since there's quite a few water Pokémon available in each game.
I don't have a particular favorite type or anything, I just choose whichever starter looks the best or would be most beneficial throughout the game ;w; But through mostly chance, I realize I do mostly pick water starters orz
I tend to choose fire starters first for some reason, though I occasionally go with a different starter if I think their final design looks better. The only exception to this is in Red/Blue where I favour Squirtle.
I choose based on final evolutions if I know them. Other than that, I'll decide on the base form. I prefer design over use or type~
I usually just choose whichever final form looks the best design-wise to me, heheh. Greninja was a very pleasant surprise; I was originally going to choose Fennekin, but the ninja frog stole the spotlight XD
I always choose water type starters. Always always always. It's just my thing it seems, ever since I started playing my first game, and also because all the water type Pokémon look really cool.
I try to mix things up and try each of the starters at least once but more often than not I end up picking whichever is the fastest/hardest hitter or has a particularly interesting design. I tend to go for monotype runs when I'm replaying so more often than not I'll end up ditching the starter anyway (normal type is my go-to~).
I usually pick the one I like most design wise, but it varies a lot and I don't really like too many of the starters. I generally choose fire if all else fails - they're pretty powerful early game and I can usually catch something more interesting or that I connect to more over the first handful of routes.