480p is the lowest form of "hi-def"(not even considered HD) and is what most games on the Wii run.
Honestly, any TV that supports 480p will do you good. If I'm not mistaken, as long as the TV has the red/green/blue outlets on the back next to the red/yellow/white support 480p. It'll show the highest quality that Wii games can be in. You'll have to get HD cables for it, though.
I think most Standard TVs come with the outlets in the back.