This gen, I've only counted those on 360 BTW, we've had GTAIV, GoW, Halo 3, Fallout 3, Fable 2, Mass Effect, CoD4, Portal(Orange Box), Dead Space, The Darkness, Left 4 Dead, Bioshock, Oblivion, Crackdown, Dead Rising, within the first 4 years. Only slightly more over 4 years but that's arguably because the tech is harder to get to grips with with dev's contending with HD visuals etc. Worryingly though, most of them are shooters.
Never mind, I'm still waiting on ME2, Thief4 and the next Oddworld. And if at least one of them lives up to my expectations then this gen will be complete for me.