1. Deus Ex: Human Revolution
2. Oblivion
3. Mass Effect 2
4. Skyrim
5. Dragon Age Origins
6. Mass Effect 3
7. Uncharted 2
8. GTA V
9. Portal 2
10. Bioshock Infinite
Edit- added next 5:
11. God of War III
12. Witcher 2
13. Fallout 3
14. Last of Us
15. Metal Gear Solid 4
Worth mentioning: Tomb Raider, Far Cry 3, Uncharted 3, Call of Duty 4