I've said this time and time again.
The Wii userbase buys the "crap" that 3rd parties keep putting on the system.
When they decide to make an effort, the effort usually doesn't seem to pay off. Cases in point, MadWorld, The Conduit, Red Steel 2. I could go on and on. Why would you put time, effort and money into a big Action Adventure (for example) title when you can put minimal time, effort and money into a game like Carnival Games that the Wii userbase will just eat up?
It now also seems they don't want Nintendo's core efforts all that much (See Punch-Out!! and Metroid Other M, which is far below Nintendo's expectations)
It honestly also doesn't help when Nintendo themselves only ever seem to advertise the system to children, old people, people having parties and mums who want to get fit.
Nintendo are as much to blame for the Wii's 3rd party situation as anyone else. When you purposely put your full attention on a certain market for 4 straight years, what do you expect developers to put on your system? At least Sony and Microsoft advertise the PS3/360 to both "core" and "casual" crowds with games ranging from Uncharted/Halo/God of War/Gears of War to games like Little Big Planet/Viva Pinata/EyePet/Banjo Kazooie.
