My mind says Pokemon, but my body says Call of Duty. Do I really have to choose?
Pokemon: Blue, Gold, Silver, Crystal, Ruby, Sapphire, Emerald, Fire red, Leaf green, Diamond, Pearl, Platinum, Black. (only reason I have so many is because my brother would buy the opposite one).
Call of Duty: Call of Duty 1, Call of Duty: Finest Hour, Call of Duty 2 CoD2: Big Red One, CoD3, Cod4, CoD: WaW, CoD: MW2, CoD: Black Ops, and CoD MW3 when it comes out.
EDIT: Actually Pokemon should win because I just remembered that I had Pokemon Colosseum and Pokemon Battle Revolution as well as Pokemon Pinball for the Gameboy Advance.