"So tell me, why are third parties not making big core games for the Wii? Some of them even fail on the HD consoles, but that doesn't stop third parties from making more for those systems (provided the studio doesn't get closed down afterwards). So it's not like a possible failure would count as a valid reason not to try."
It isn't. The PSP is less powerful than the Wii, sells even less hardware*, and developers still support it with their major franchises more.
* Nothing against the PSP, since it has several games I want when I can get the system.
A flashy-first game is awesome when it comes out. A great-first game is awesome forever.
Plus, just for the hell of it: Kelly Brook at the 2008 BAFTAs