It's refreshing to see that the software industry isn't the only place where Gartner has no clue - listen to them on the Wii:
The newly published article cites Van Baker of analyst firm Gartner suggesting of the Wii: "Its appeal is primarily to casual gamers, and there's a serious question about how long casual gamers will stay engaged with the platform... It wouldn't be surprising to see them lose interest after a relatively short amount of time."
I suspect that Baker has never used a Wii, or attended a party where one is around. The Wii gets everyone engaged - serious game players and casual audiences. The Xbox and PS3 pretty much hit one demographic: the hard core.
The last time I looked, the hard core gaming crowd wasn't as big as the casual one, but hey - that's a complicated thing for a Gartner guy to wrap his head around - he might have to engage with the real world, or something.