The most pirated game in 2011 was a PC shooter, but it wasn't Modern Warfare 3.
With 3,920,000 copies downloaded through bittorrent, TorrentFreak reported that Crysis 2 was the most pirated game in 2011. Call of Duty: Modern Warfare 3 came a close second with 3,650,000 copies and Battlefield 3 followed with 3,510,000 copies. The PC versions of FIFA 12 and Portal 2 took the 4th and 5th locations.
As expected, PC games were pirated much more than their console counterparts. The most pirated Wii game was Super Mario Galaxy (1,280,000 copies) which was in fact released in 2010 and the most pirated Xbox 360 game was Gears of War 3 (890,000 copies). Torrentfreak didn't report PlayStation 3 games piracy statistics.