Kanto - I've never actually played a Kanto game :( But i want to get Blue for the 3DS, in which I'll get Charmander!
Johto (SoulSilver) - Chikorita! (Sydney) <3 She was a female, too!
Hoenn (Omega Ruby) - Treecko! (Vern) I was actually having a lot of trouble choosing which starter I wanted...but then Mega-Sceptile dropped and it was so beautiful that the decision was made. <3
Sinnoh - Piplup (aqua) on Diamond, my first-ever Pokemon game; then Chimchar (Infern) on Platinum. I later did another playthrough of Platinum with Turtwig (Gaius) - I don't really have one Sinnoh Pokemon that I look at and feel like, "yes, that one's my partner! <3" like I do for other gens; Infernape would probably be the closest because my original Platinum team was special to me.
Unova - Oshawott (Kawa) in Black (OF COURSE), Snivy (Sera) in Black 2, who was female
Kalos - Fennekin! (Flicker) I had serious sparkly-eyes for Fennekin at the time, haha. i recently began a new game where I chose Froakie (Raspberry), but the Fennekin line is still the most "iconic" for me.
Alola - Due to getting both versions for the first time, I actually got to use all three starters! Rowlet (Haumea) in Moon, Litten (Regulus) in Sun and Popplio (Georgium) in Ultra Moon.