Actually, didn't Nintendo release some demographics recently showing that the majority of their Wii audience was STILL males, smack dab in the core player age range, and that they played many hours a week?
As for the spin-offs, Yes, the rules for the market leader are changing are changing. But they're changing in that games can be ported less and less successfully. I actually welcome the spin-off route. If that means that we're getting original Wii games designed specifically for the wii controls, and not "watered up" from a PS2 build, then yes please! I'm still torn on the issue though...after all, I have Alone in the Dark on pre-order for the Wii, and that's an obvious port!
As for general third party support... well, I'm hoping that Ubisoft follows THQ's example. THQ is making some really AMAZING traditional titles for the Wii, from de Blob, to Deadly Creatures. Ubisoft may not be the shining light of exemplary traditional third party support (still waiting on Red Steel 2, and done WELL this time please?), but there are such examples starting to emerge.