The wii has a lot of good games as does the 360. Personally, I am a huge nintendo fan so I have a wii.
A few things you need to take into consideration:
Graphics/gameplay-do you care about great graphics or fun gameplay more?
Titles out- both systems have a lot of good titles out.
Upcoming games-I haven't looked at the 360's upcoming games but I know the wii has some really cool on the way.
I'd go with the wii. It has a lot of really fun games. The 3rd party was weak at first but getting stronger. Plus, it has Brawl
