1. Uncharted 2: Among Theives
2. Assassin's Creed II
3. Grand Theft Auto V
4. Mass Effect 2
5. Red Dead Redemption
6. The Last of Us
7. Gears of War 2
8. Lost Odyssey
9. Kingdom Hearts: Birth by Sleep
10. Total War: Shogun 2
11. Uncharted: Drake's Fortune
12. Crisis Core: Final Fantasy VII
13. inFamous
14. Mass Effect
15. Gears of War 3
Could also include Uncharted 3, Gears of War, Mass Effect 3, Deux Ex Human Revolution, XCOM, Halo Wars... I feel quite uncomfotable condensing about 8 years of gaming into 15 games, but Uncharted 2 is a very clear winner
I could probably go on editing the rest for weeks
EDIT: forgot CoD 4... a bit late, but it should definitely be on the list