LeafGreen: Charmander
Crystal: Totodile
Sapphire: Torchic (and a friend who was starting a new game got me a fresh starter Treecko).
Ruby: Mudkip
Diamond: Chimchar
Pearl: Turtwig
Platinum: Piplup
Black: Tepig (and managed to oh so luckily get an Snivy from GTS. Lucky that it wasn't in exchange for a level2 Reshiram or what have you).
White 2: Oshawott
I'm thinking Fennekin for Pokemon X.
And if I get Y afterwards, I'll try with Froakie, I think.
And if I don't get one through GTS or other means, then I'll get Chespin from Pokemon W/Z or whatever they call it, if they do one.
Overall, I like to choose Fire types.
It's normally my first choice.
But I'll try other starters on another game, or get one from a friend or online.