1 - Mass Effect 2
2 - The Elder Scrolls IV: Oblivion
3 - Gears of War
4 - Super Mario Galaxy
5 - Bioshock
6 - Uncharted 2: Among Thieves
7 - Vanquish
8 - Dead Space
9 - God of War 3
10 - Assassin's Creed II
Notable mentions: Alan Wake, Amnesia: TDD, Borderlands 2, Final Fantasy XIII, Enslaved: OTTW
I deliberately avoided more than one game of the same franchise for the sake of diversity and preventing bias.