I'll go along with Crackdown as the most underrated as well. Played that game to death and loved every minute of it. The catch was getting powered all the way up and then going crazy. I still remember climbing all the way to the top of the main tower just to jump off. Good times.

Overrated I will go with the Black Ops games. My daughter plays them regularly but they just don't scratch my itch.

The most fun I've had with games this gen would be (in no order): Minecraft, Fallout 3 (loved the DC wasteland theme), Borderlands (both of'em), Skyrim (of course) and Dead Island.