Guitar Hero (and clones) might be fun, but it's like Facebook...more people use it with negative consequences. For example; it's very convenient to arrange a meeting via a social network site, but "having" meetings over social network site slowly turns you into a sociopath. To draw an analogy, kid that wants to learn guitar and fails over the first obstacle could find his savior in GH, because of his imagination.
Every kid that plays GH or Rock Band or whatever could be playing a real instrument. If you want to argue that GH could just be the right thing to produce a certain curiosity for the real instrument, and could motivate kids to go for real guitar, it' just like Facebook...most of 'em won't. Why? Why they don't ask girls out on the real date via Facebook? Because it's helluva easier to lead some sort of imaginary thing going on. Try it in real life. People are afraid of failures, and most kids today don't have strength to carry on after breaking a leg.
Rant mode off.
Actually, i've played some game called Raving Rabbits (or something like that) on friend's Nintendo Wii. You can dance and do all sorts of stuff with two Wii controllers, and you can also play some songs. I took the drums, and since i'm a musician (and we do have a sense of rhythm...don't we?) and i also know basics of real drumming, i kicked ass on my first play. My friend, who's not a musician, played keyboards (you're moving controllers like timing of notes, not simulating real notes) and he was also very good. Now, keyboards were on tougher level than drums, since they feature more variety in patterns. So on next level we switched. We were terrible, and that's when i realized how multiplayer in the game can be tricky. He missed drum timings badly, and i couldn't concentrate on rhythm in my head, was mislead by his drums and sucked big time
P.S. it would be fun to try the dance mode in the game, but two guys home alone dancing with Nitendo Wii to "Ladies Night"...