Sales thus far (Famitsu)

– Mario Kart DS (NDS, Nintendo): 2,935,577 units sold
Release: 12/08/05

– Wii Sports (Wii, Nintendo): 2,853,740 units sold
Release: 12/02/06

– New Super Mario Bros. (NDS, Nintendo): 5,136,819 units sold
Release: 05/25/06

– Animal Crossing: Wild World (NDS, Nintendo): 4,630,850 units sold
Release: 11/23/05

Source