I don't think the intention is to bad-mouth Guitar Hero. Just lamenting the fate of poor, overlooked Guitar Freaks. Even if it were to make a comeback, it wouldn't be able to shake the stigma of being a "Guitar Hero ripoff." Ironic, no?
But you're right, this is extremely normal in the games industry; it's how genres are created. With Rock Band coming out, and Jam Sessions just released, perhaps a trend is starting, and in a couple years "instrument simulator" will be a persistent subgenre of the rhythm-action game.