Buoyed by the launch of two Mario titles, Nintendo's 3DS has hit the same four million units sales figure in the United States that it recently reached in Japan. The Kyoto-based company can always rely on that rotund Italian plumber — Mario Kart 7 and Super Mario 3D Land have been the fastest-selling Mario Kart and Super Mario games ever, at over a million copies each. Wii title The Legend of Zelda: Skyward Sword has also reached the one million mark, becoming the 45th release on Nintendo's home console to do so. After a difficult year and some tough price drops, it looks like Nintendo and its 3DS may finally have some momentum going into 2012.