[b]Underrated[/b]

Advent Rising - the story was intriguing and the gameplay was solid as fuck

InFAMOUS 2 - pretty much improved on the original greatly, with some awesome new mini powers. 

Gungrave - an arcade shooter that has a ton of spirit and a badass boss battles. Also the original version of the fantastic anime adaptation.

[b]Overrated[/b]

Skyrim - the world, for how big it is, is mostly empty. Main story is boring, most of the side stuff too. Melee combat is a joke.

Super Mario Galaxy 2 - it's just a rehash of the first one but without a good hub world.