I'll put on my list not only the games released in 2011 but also those old ones I played in 2011.
RPG only list:
1. The Witcher 2: Assassins of Kings
2. The Legend of Zelda: Wind Waker
3. Deus Ex: Human Revolution
4. Okami (How could I forget this one?)
5. The Legend of Zelda: Skyward Sword
6. The Elder Scrolls V: Skyrim
There are some I'm still playing like Bastion, Tactics Ogre, To the Moon, Chrono Trigger (yeah, I should've finished it by now), Persona 2, Xenoblade, Professor Layton 4 and Nier. (Also Corpse Party if it counts as an RPG)
Like we all here, although I'm a big RPG fan my favorite game of the year was Portal 2
My biggest let down was 3rd Birthday. What a horrible mess of a game and a missed opportunity to bring the series back.