Call of Duty 4

CoD4

This is a difficult one...

Mario Galaxy is the most likely for me, but this gen has so many defining games already, it's difficult to choose. Bioshock, Uncharted, Gears (my #2), and Dead Rising.

I played Galaxy the most, but I have more sit down and play fun with Link's Crossbow Training.

Between CoD4, Crysis, Bioshock, Stalker, UTIII, Gears of War;
the very best was S.T.A.L.K.E.R.

(I played only FPS on my PC this year but next month I'll Buy a PS3 or an Xbox to play GTA IV).

If I had to pick just one... Mario Galaxy

Ratchet and Clank ToD, one of the best games i have ever played.

 Yeah that game is awesome.

Bioshock is the best I've played this gen.

Legend of Zelda: Twilight Princess

I'm sorry but if there is a Zelda console game in a generation it automatically wins. I mean you can't compete with Zelda imo.