Super Smash Bros. Brawl was probably the most fun. Good times playing that in my dorm's common room with whoever happened to be there at the time. Loved everything, from some hardcore 1v1 to joke "GvG" (Ganondorf vs. Ganondorf) matches.
Kinda burned out on that game now, though.
Also had a lot of fun with Donkey Kong Country Returns, Super Mario Galaxy, Xenoblade Chronicles, and Uncharted 3. All great games.
Edit: Also have to agree this gen has been freaking incredible. We've gotten the two greatest 3D platformers, one of the best JRPGs of all time and countless other gems. Plus all the unique small/indie games.
Oh, also one of my favorite 2D platformers, Rayman Origins. I love the artwork and how that game just flows when you get in a rhythm.
Oh shit, I forgot about Infamous 2, also. My favorite open world game ever. At least until I play Sleeping Dogs, because that game looks freaking fantastic!