Red Dead Redemption The Orange Box Portal 2 Halo: Reach Limbo Assassin's Creed 2 Mass Effect Mass Effect 2 Mass Effect 3
More than I expected, honestly. Also, I just started Arkham Asylum, and I own but haven't started Arkham City, Dark Souls, and Fallout 3. Just from what I've heard of those games, I fully expect at least one or two of them to become all-time favorites for me, so I voted 10-20.
Halo 1 LAN vid: http://www.youtube.com/watch?v=VhjWnJU2EKY