My top 10 -
1. The Orange Box
2. Mass Effect 2
3. Uncharted 2: Among Thieves
4. Red Dead Redemption
5. The Last of Us
6. God of War III
7. Heavy Rain
8. Grand Theft Auto V
9. Assassin's Creed II
10. Journey
There are some others I'd like put on the list.. but these, (I feel) are the games that defined last gen for me.