Blows me away that LA Noire beat Skyrim. And Batman.
I guess it's because LA Noire had problems on the PS3, and 360 was the only other platform (at launch) so it got the bulk of the players. Whereas many people got the PC version of Skyrim, and the PS3 version of Batman was OK, so the 360 wouldn't dominate as much for those games.
I think part of it is also L.A. Noire has been out for 8 months or so, while Skyrim isn't even 2 months yet. I'm fairly positive Skyrim will pass it someday, but these stats were based on what was played in 2011. It's not exactly fair I guess, but it is what it is.