I would suggest:

-Mario Kart Wii
-New Super Mario Bros. Wii and 2
-Sonic Colors
-Legend of Zelda: Twilight Princess and Skyward Sword
-No More Heroes 2: Desperate Struggle
-Monster Hunters

Not to mention you can also download games from previous consoles so consider other games as well.

If you're going to get Mario Kart Wii then I highly recommend getting the steering wheel that you put on the controller. It seems stupid at first but it actually improves your game play.
If you're not really into racing games but still like speed then I recommend Sonic Colors. It's really fun and I recommend playing the game with either the nun chuck or the gamecube controller. Out of those two I recommend the gamecube controller for the best control. The game is awesome, though, since it works with every controller for the Wii.