The thing with wii is that there are so much stupid party games which sell so good so for nintendo no reason to bring out something else.
Mario Kart also suffers from his problems. I got everywhere 2 star rating but getting 3 star is just pure luck. Then you got the rubberband cpu but I found no trouble with that as I am good in mario kart and beat cups almost everytime with ease, but it does not matter how much skill you got, getting hit by three spikies in a row makes everyone lose. Online suffers from a new hit as you had snaking in ds now in online you got wheeliespam and bike is so overpowered compared to karts. Karts have no advantage over bikes and if you want to win serious games you are forced to get a bike. God how many times I saw baby daisy/magikruiser, daisy/mach bike and funky kong/bowser bike.
So far wii does it average and brawl will not be good in mp so don't get your hopes up as many say online it sucks hard with the horrid lag and other problems, however the sp is good they say.