Mario Kart DS was the game that finally ushered Nintendo into the Internet era. Utilizing Nintendo's new and free Wi-Fi Connection service, you can finally play Mario Kart against anyone in the world. The software for accessing the network is a bit primitive, but it was definitely a leap in the right direction, and after the initial setup, is extremely easy to use. But the truly amazing thing about Mario Kart DS is how much more it does than previous Mario Karts. Aside from the usual 5 cups (including the Mirror Cup) and Battle Mode, Nintendo added the Retro Cups, allowing us to play many of the excellent tracks in previous Mario Karts, and a single player Mission Mode which provides quite a bit of replayability.

Runner Up: Castlevania: Dawn of Sorrow