Actually, now that I think about it, it's probably Pokemon lol. Got Red, Blue, Yellow, Gold, Silver, Crystal, Diamond, Stadium, Stadium 2, Snap, Rescue Team, and Hey, You, Pikachu!
If you only count one genre in a series, then it would go to Mario platformers,, I'd have to say it's Mario for me, with nine games (six on the Wii alone XD). Got the original NES cartridge of Super Mario Bros, Super Mario Land on Game Boy, New Super Mario Bros DS, all three Wii platformers, as well as World, 64, and 3 on Virtual Console.
Also of note: All five Ace Attorneys, MGS 1-4, Halo 1-3 and Reach... that probably covers it for me.