All I'll say is that the market defines what it wants for the most part - 'next gen' is just marketing and hey we have three new consoles, nothing more.
The only difference I see between Wii and 360/PS3 is that of HD graphics potential.
There's no reason the Wii couldn't have the same types of games the 360/PS3 has (designed for its spec of course) while in principle there's nothing to stop you sticking motion sensing, etc. on 360/PS3 (actually Sony already tried this in a quick and dirty way called the SIXAXIS).
Right now I'll accept that for some demographics there is no direct competition - I doubt all those COD4 and GTA IV owners spent too long looking at Wii and/or 360/PS3 and stroking their chin trying to decide, equally I'm sure some Wii owners never considered anything else.
But what we can see is clear, more people want what the Wii offers. If you combine 360/PS3 sales quite a large percentage of gamers clearly want HD graphics instead.
They are all however 'this gen' of consoles as in they are the latest console on sale from each vendor.
Wow - can't believe I bothered posting this. This thread has no point - it's like saying that this years Samsung TV is somehow competiting with last years Panasonic TV but not this years Panasonic TV.
Try to be reasonable... its easier than you think...