On a Nintendo platform, everyone follows Nintendo's lead
Well then there's your problem. Maybe third parties oughta grow a pair and make their own games instead of just making cheap knockoffs of stuff. And besides, when Nintendo made a majority of "core games," like Zelda, Metroid, and SSBB, and with stuff like RE4 and hell even the Call of Duty games pulling down millions, they didn't say "Hey, now THERE'S an opportunity, we need to put, say, FIGHTING games, because there is a huge market for fighting games on Wii, what with the highest selling and most popular fighting game of all time, SSBB, being for the system." They usually say something about how they can't "beat Nintendo" or something.
So when Nintendo makes core games, third parties just ignore it or run around yelping about how "Only Nintendo games sell on Nintendo systems, we can't compete, BAWWWWW!" And when Nintendo has some core game downtime (as it takes time to make those games, as opposed to say, Wii Fit), it's all "Whelp, just goes to show, Wii is non-games for non-gaming grandmas." It's like they were already looking for a reason to not make Wii games, and then they found one. And you say this like 3rd parties have had great success aping Nintendo's games like Wii fit and Wii Sports, when they really haven't. EA Active might be a small success at around a million right now, but Wii Fit has sold somewhere in the 20 million range.
Nintendo is not to blame for third parties. Seriously. They have had AMPLE opportunity to create high quality games for the Wii and attempt to market them, but they've either ignored the market or threw around stereotypes/demographics/downright insults to Wii owners. It's like you are trying to blame a hip, cool kid at school because a lot of people try to cramp his style and failing at it. Maybe if third parties would just BE THEMSELVES instead of Nintendo-Lite or bitching about how Nintendo's popular, they'd have better reputations. Take, for example, Monster Hunter 3 in Japan, highest selling third party game this generation there. Core game, Wii. And this isn't a "casualized" or "focus-tested" Blue-Ocean blahblahblah Monster Hunter. It's just Monster Hunter 3.
An earth-shattering world crumbling is Factor 5 closing up shop. Karma is my favorite thing in the entire world.
That's not nearly as gratifying as GRIN closing up. It's like somebody wrote a fanfiction about being a Wii fan and seeing this actual Wii-hating developer (The president had quotes as such) go from major mover on the PS360 front to choking on its own blood after three straight failures, one a complete destruction of a beloved NES classic by making it some kind of "Mature" game mutant.
Ooo~ Get goosebumps just thinking about it.