Part of me wonders whether this is just a chicken and egg scenario. What came first; shovelware that wouldn't satisfy the hardcore gamers, or an audience that is totally devoid of a hardcore contingent? As many people have said, the Wii has sold millions of units since its release, are we really to believe that there wasn't a single hardcore gamer who bought one of these consoles?
When the Wii first came out, the majority of the third party games where either just crappy PS2 ports or original (yet uninspired) titles with motion controls tacked on (and barely functioning in some cases). It feels to me that the third parties were basically pushing the kiddy shovelware on the Wii when there was an audience for hardcore/mature titles, choosing to focus on the graphical dick-swinging contest between the Xbox and PS3 instead, eventually leading to that audience abandoned Nintendo's console in the face of all this craptitude.
Whilst all this was happening, Nintendo (being the company that actually developed the console, of course) were the only lot who were making games that fully utilized the Wii's capabilities. Customers quickly picked up on the message; Nintendo games, good, recommended purchase. Third party games, broken, stay the hell away.
Now, the third parties have finally started putting out some decent games (in some very niche genres, I hasten to add... on-rail shooters? Really*?), and now they are complaining that there is not an audience to buy their game? Sorry, but from where I'm sitting, they really only have themselves to blame.
You can't starve a person and then complain when his corpse doesn't eat the five course meal you've spent all day cooking.
(*Actually, I really did enjoy Dead Space Extraction and those two Resident Evil games... But the point still stands!!! Oh, and that House of the Dead Overkill was also pretty awesome... dammit)