Mario Kart 7 didn't have much time to make an impact in sales last year, but it still managed to be the best selling game in Japan for 2011. The Nintendo Wii racing game was only released in early December.
Below is the rest of Japan's top selling games in 2011 and as you can see, it was quite a year for Nintendo, which had six of the top ten selling titles.
01. Mario Kart 7: 1,082,391
02. Super Mario 3D Land: 1,042,511
03. Monster Hunter Portable 3rd: 1,021,457
04. Monster Hunter 3G: 809,322
05. Final Fantasy XIII-2: 697,146
06. Final Fantasy Type-0: 696,428
07. Minna no Rhythm Tengoku: 633,429
08. Tales of Xillia: 632,151
09. Wii Sports Resort: 612,807
10. Wii Party: 584,545
[Source: Official Nintendo Magazine]