Valkyria Chronicles with 30 hours.
still sad that part 2 and 3 aren't on consoles....

Ni no Kuni, I think.

MGS4. i was bummed out it didn't come to the 360 like most other series did aat first but damn am i happy i got one, Infamous and Infamous 2 are some of the finest games of last gen IMO.

Skyrim. It is one of the best games I have ever played.

LBP and LBPkarting (yes i'm fan) : creating and playing created levels takes a loooooooooooooot of time.

Singe player: Red dead redemption.
Multi player: Uncharted 3.

for me i'll say Resistance: Fall of Man because of how i always play split screen offline whenever i have friends over.

also God of War 3 since i finished it 4 times and i'm in my 5th playthrough

and finally Uncharted 2 coz i finished it 3 times and casually play every now and then.

Bioshock - my favorite game of last gen. I've also achieved platinum on Uncharted 1 and 2 as well as the three main God of War games.

MW2 - Around 600 hours. New games in the franchise are boring or am quite burned out. Guess bit of both.