ha i find that hilarious the it is considered a commercial failure and sold 2.5 million copies

Like Chinatown Wars. "It should have sold more!" is irrelevant to the company. Whether it makes money does.

But Nintendo did admit they didn't hit the mainsteam as with Wii Fit, but that is not the same as being a commercial success or failure.

No more heroes is one of the greatest games on wii and yet many peopel don't know about it, and zack & wiki, there's another under rated game

That's overlooked, not underrated.

I need to pick up Wii Music at some point. I am sure I will have fun with it.

I agree with most of the games that have been mentioned here. One game that hasn't been mentioned and that I consider to be underrated:

Destroy All Humans: Big Willy Unleashed. The game is really fun and its only downside, IMO, is that it is only 8 hours long. Now, considering it's only 15 to 20 bucks I think it's a decent buy.

Sometimes reviewers take into account the cost of the game when they give a game its score. I would have been very disappointed if I had spent 50 bucks on that game, because of its length, but now that it is cheaper it's not like they're going to go back to the review and change the score...

The same thing happened to Harvey Birdman's game and to a lesser extent to Worms: A space oddity. I mean, the worms game is definitely worse than the pc version, but it got hit hard because of its price and lack of online multiplayer.

I think the sweet spot for these kind of games is $20. They're good, just not $50 good.