I'd say you should do two things.
1) Look at the library of Wii games. There are a lot of great ones, especially if you like platformers (Galaxy 1/2, Donkey Kong Country Returns, Kirby Epic Yarn, NSMB Wii), Nintendo's first party games in general, or you're looking for a good family experience. You can also get a lot of great Wii games on the cheap. Muramasa is 10 bucks on Amazon, Red Steel 2 and No More Heroes are 15.
2) Watch Nintendo's E3s press conference.
If you can find between 5 and 10 Wii games you'd really like to try, I'd say the Wii will be worth it. If you find 5-10 games you'd really like to try AND you're impressed by what Nintendo shows at E3, wait. If you don't find 5-10 games you like, then I'd forget about the Wii altogether, unless you'd like to pay about 200 dollars to try Xenoblade.







