1st Gen: Red, Blue, Yellow
2nd Gen: Gold, Silver, Crystal
3rd Gen: Ruby, Sapphire, Emerald, FireRed, LeafGreen
4th Gen: Diamond, Pearl, Platinum, HeartGold, SoulSilver
5th Gen: Black, White, Black 2, White 2
6th Gen: X, Y
6th Gen Upcoming: OmegaRuby, AlphaSapphire
There's a split between 2nd...