Xenoblade. I expected a good game based on the hype, but I was blown away. Further, I was amazed that a game on Wii could impress me so much. I haven't enjoyed the SD visuals much since I got my 360. But when a game you think will be good is among the best of all time? Blown away.

kid icarus

Metal Gear Solid
Mass Effect
Uncharted 2 - Bought both games and played them back to back. First game was great, but the second blew me away.

Kid Icarus Uprising

"didn´t expected to blew you"

On topic: The original Uncharted. I wasn't a fan of Crash during the PS era, and never played a single Jak & Daxter game. So I wasn't what you can call a Naughty Dog fan.  Uncharted changed that. Uncharted 2 did it again, and has become the game of the gen for me.

Xenoblade, Monster Hunter and Endless Ocean 2.

Red Dead Redemption. I bought the game on a whim, I didn't really know anything about it and good god it might be my favorite game of this gen.


BONUS (mobile game):

If you have an iPhone, I highly recommend that you download Solitaire Blitz. Its a quick puzzle game but its soooo addicting and fun. I usually don't find free mobile games to be that great, but its such a good time killer (its made by PopCap)

Nier

SM3D Land: Didn't expect much but wow!
Fifa 09: My cousin made me play it, was still anti FIFA and pro-PES. Haven't turned back since
Uncharted 2: Incredible game!

Most recently it was Retro City Rampage, Wipeout 2048, and Resident Evil: Revelations. Three of the best games of 2012.

Before that? Games like Wii Sports Resort, Killzone, and, believe it or not, Tak and the Power of Juju.