Deus Ex Human Revolution. The prequel to one of the best games ever made, it's such as shame that it was incredibly overlooked in 2011. It had everything going for it: atmosphere, great characters, an excellent music score, and open gameplay that stayed fairly true to its roots(except for those crappy boss fights). And there's a possibility for another game.
That's funny, I just posted a review titled "one of the most underrated games of all time". http://www.gamefaqs.com/gamecube/917888-freedom-fighters/reviews/review-153414 Technically a last gen game, but it's sort of related.
In an insane world, a sane man must appear insane.
The Saboteur is usually my pick in topics like this. Incredibly fun game, interesting setting and use of color, great lead character.
However, I'm tempted to give it to Fishing Resort on the Wii because that game gets almost no attention or love, yet is a really amazing game. The fishing comes closest to capturing the fun of real fishing of any game I've played, and there is a lot else to do besides fish. It is one of those games that, if you saw it on the shelf, your first thought might be "Shovelware!" but it is anything but.