Starters

[icyraven93]

Generally, it ends up going like this.

Gen 1 Games + Remakes: Bulbasaur or Charmander about equally (except in Yellow, where Pikachu's my starter Pokemon instead)
Gen 2 Games + Remakes: Cyndaquil
Gen 3 Games + Remakes: Mudkip
Gen 4 Games: Turtwig
Gen 5 Games: Oshawott
Gen 6 Games (if I ever get one): Froakie

 

[Curtkid]

Well...here are my picks:

Gen 1: It should be obvious (Charmander).
Gen 2: Totodile, love that blue alligator!
Gen 3: Treecko, a grass salamander that becomes a grass raptor? Sign me up!
Gen 4: Chimchar, it's kinda like Charmander, but a monkey, and who doesn't love monkeys?
Gen 5: Snivy, yes, I named it Smugleaf and kept it unevolved, feel free to judge me,
Gen 6: Froakie, because Ninja Frog,

 

[Sylvious]

Gen 1: Charmander, cause Charizard is awesome.
Gen 2: Cyndaquil. Yes, you can see where I'm going with this.
Gen 3: Treeko, I tricked you. <
Gen 4: I never really liked the Gen 4 starters, but I still chose Chimchar.
Gen 5: I have no idea since my Pokemon Black version cartridge is stuck in a box in my attic. I think Snivy?
Gen 6: Froakie, cause every other Gen 6 starters Imo sucks.

 

[Magos Amphrose]

I: Bulbasaur, my first ever Pokemon.
II: Chikorita, because kawaii.
III: Mudkip because Ground/Water type.
IV: Piplup because I always imagined it tsundere.
V: Oshawatt because it's a water-ninja-bear.
VI: Fennekin because it's fluffy and because Fire/Psychic type.

 

[Ashtonator]

gen 1: charmander, my first pokemon
gen 2: totodile, because he is kawaii
gen 3: torchic, because cute as torchic awesome as blaziken
gen 4: chimchar, he was the first pokemon I have seen
gen 5: oshawott, he is cute
and gen 6: chespin because chestnaught is to bolky

 

[TrimGuide4662]

Blue - Bulbasaur.
Silver - Cyndaquil.
FireRed - I first started out with Charmander, but after restarting my game a few times, I settled on Bulbasaur.
LeafGreen - Squirtle.
Ruby - I had originally started out with Treeko, but after I had gotten to the Elite Four, my cousin got a hold of my game and restarted it (pissed me off so bad) so I ended up with Mudkip.
XD: Gale of Darkness - I went with Eevee's Psychic evolution, Espeon.
Diamond - Chimchar.
Pearl - Piplup.
Platinum - Piplup.
Black - Tepig.
White 2 - Tepig.

 

[Skycraft]

In Leaf Green, I chose Squirtle.
In Heart Gold, I chose Totodile.
In Omega Ruby, I chose Mudkip.
In Pearl, I chose Piplup.
And in White, I chose Oshawott.

I don't really like water types as you can see.

 

[smew178]

I always go with the water types.

 

[Cáscara Olas]

In Alpha Sapphire I chose Treecko
In X I chose Chespin
In Sun I chose Rowlet
In Ultra Moon I chose Poplio
In Shield I chose Scorbunny

If I were to chose for other games it would be

Bulbasaur in Kanto games (Excluding lets go and yellow)
Totodile in Johto games
Treecko in Hoenn games
Chimchar in Sinnoh games
Snivy in Unova games

 

[Merciless Medic]

Well lessee here:
Blue: Charmander
Green: Bulbasaur
Yellow: Pikachu (duh )
Silver: Totodile
Sapphire: Treeko
FireRed: Charmander
LeafGreen: Squirtle
Diamond: Chimchar
Pearl: Turtwig
Platinum: Piplup
HeartGold: Cyndaquil
SoulSilver: Chikorita
Black: Tepig
White: Snivy
Black 2: Snivy
White 2: Oshawott
X: Fennekin
Y: Chespin
OmegaRuby: Mudkip
AlphaSapphire: Treeko
Sun: Litten
Moon: Popplio
Ultra Sun: Rowlet
Ultra Moon: Popplio
Let's Go, Eevee!: Eevee
.... and that's all I got XD

 

[Scrafty]

Me
Red: Charmander
Blue: Squirtle
Yellow: Pikachu
Heartgold: Cyndaquil
Soulsilver: Totodile
Emerald: Treecko
Diamond: Chimchar
Platinum: Piplup
Black: Snivy
White: Oshawott
X: Chespin
Y: Fennekin
Sun: Litten
Moon: Popplio
US: Litten
Sword: Scorbunny

 

[Fraised]

Hmmm...

Blue: Bulbasaur
Gold & HeartGold: Cyndaquil
Emerald: Treecko
OmegaRuby: Mudkip
Diamond & Platinum: Piplup (and Chimchar on one uncompleted playthrough)
White: Snivy (and Oshawott on an uncompleted playthrough)
White 2: Snivy
X: Froakie
Y: Fennekin (incomplete playthrough; thinking of starting over and choosing Chespin)
Sun: Litten
UltraSun: Popplio
Sword: Scorbunny

My choices in each generation don't have a particular rhyme or reason; on my initial playthrough, I'll always just choose my favorite of the bunch. I do like to mix things up, though, so on subsequent playthroughs of the same game I'll usually try to pick a different starter.
In the case of UltraSun... while I don't mind Popplio, I'll admit that I'm not as much of a fan of it/Primarina as I am Incineroar and Decidueye. But I already had both on my single journey through vanilla Sun, so I chose Popplio in Ultra just to even out the trio.
I've not really touched Gen I, but I tend to alternate between picking Bulbasaur and choosing Squirtle, as I like the two equally.

 

[Bulbathor]

I think I'll list my initial playthroughs, and my current choices too! For my first playthroughs, I had:
Red: Charmander
Silver: Totodile
Sapphire: Mudkip
Fire Red: Charmander
Diamond: Turtwig
Soul Silver: Totodile
Black: Oshawott
X: Fennekin
Sun: Litten
Alpha Sapphire: Mudkip
Shield: Sobble

In my most recent saves, I have:
Red: Bulbasaur
Silver: Totodile
Sapphire: Mudkip
Fire Red: Charmander
Diamond: Turtwig
Soul Silver: Totodile
X: Fennekin
Sun: Litten
Alpha Sapphire: Mudkip

I haven't bothered replaying Black or Shield because I don't like them as much as the rest. However, as you can see, I'm a Mudkip Loyalist. XD

 

[glaman5266]

Red: Bulbasaur
Silver: Chikorita
Crystal: Cyndaquil
Ruby: Treecko
Platinum: Piplup
I skipped Gen 5...
X: Chespin
OR: Treecko
Moon: Popplio
Sword: Grooky

I typically favor the grass types, though I've tried Squirtle, Charmander and Turtwig in the past. Despite this, Cyndaquil is my second favorite starter behind Bulbasaur. Thunderpunch Typhlosion is so good in gen 2.