The Wii is fine...as long as you go in knowing what to expect.
Like ALL Nintendo home consoles from the last 2 generations, you buy it for one major reason: First part Nintendo games.
There's some good "second party" stuff too like DKC and Metroid, but for the most part, you buy a Nintendo console for the likes of Zelda, Mario, etc. If you enjoy those style of games, there are some real gems on the Wii. Both Mario Galaxies were a blast, New Super Mario Bros. was awesome, new DKC was a heck of a lot of fun, Skyward Sword was excellent, etc.
If you're a fan of the classic Nintendo franchises, there's plenty to enjoy. If you're looking for diversity of the 360 or PS3's line-up, you'll be sorely disappointed.