Portal 2 was very good. Unfortunately there weren't any standout adventure games, except for Last Half of Darkness: Society of the Serpent Moon and Baron Wittard: Nemesis of Ragnarok. I'm not sure if Gray Matter counts as a 2011 release since it was out a bit earlier in Europe so probably not. All of those are contenders. I'll also have to reserve my final judgment until I've played Stacking. If Testament of Sherlock Holmes comes out before the end of the year, that is very likely to get my pick. The game looks fantastic.