Here is a nice article which looks at the best Wii games of 2009 which unfortunately didn't make an impact on sales charts, and it is presented without much negativity or hostility toward Wii which seems to be an increasingly rare thing these days.
http://www.gamesradar.com/f/2009s-best-wii-games-that-died-at-retail/a-2009121492359104082The stigma surrounding Dead Space Extraction is kind of a shame, as it sounds like it is a good game in its own right. I'm not personally very interested in that type of game, but I might check it out if I find it on sale or something.
Little King's Story was one of the best games released this year. It would seem most people have passed on it due to its overly "kiddie" presentation, which personally I love the style of the game but can understand why it is a turn-off. Plus, such a style belies the relatively complex game found underneath the bright and cheery surface.
ExciteBots may be my pick for overlooked game on Wii, period. Once again I think its style is what turned people away, as racing transforming animals and insects is just too goofy for most. Sadly I'll bet it would have met better sales if it were titled Excite Truck 2.
To be fair, We Cheer has gotten some decent reviews. It would seem it delivers what it promises, so I can think of worse examples of games that shouldn't sell but do. Game Party comes to mind...

and

at Sexy Poker. Even worse than its existence is that people downloaded it.
There are other games listed there that are on my to-buy list as well.