Hm, I may not recommend it as the first game you buy; it doesn't really take advantage of the Wii that much. It could really be played with an NES controller.
Zelda is really fun, but LONG and no multiplayer. 40+ hours to finish the single player game skipping all side quests. If you like deep adventure games...
Excite Truck is relatively short, but it's a blast. It's an over-the-top racing game, kind of like burnout. You steer using the Wii remote, and can go off ridiculous jumps while boosting and adjusting your pitch and angle by tilting the remote. It's ridiculous, and it's fun.
http://youtube.com/watch?v=Rny3xbuoMpo
Rayman: Raving Rabbids is something of a comedy game. It's a collection of shorter games (sort of like Wii Sports or Wii Play), but it's got around 70 of them, and it's about evil retarded bunnies that want to take over the world. Really funny. Great for multiplayer with friends, as they'll laugh like nuts at it.