I've only played guitar hero 2 and 3 but i can safely say that Guitar hero 3 is better that all of them. And then we come to the cheap imitator Rockband. I'll admit that the rockband guitar is cool, but the strum bar sucks! When you have rapid notes in a row the RB guitar strumbar doesn't come back up very quickly, so your left there pounding on this strumbar. On the other hand, the guitar hero guitar looks just as good if you put the supplied stickers on it so looks good. And on the GH3 guitar, the strumbar quickly retracts back to the top for easy rapid strumming. Not to mention that the song list on GH3 is better than Rockband's.
Basically Rockband is a crappy imitator to the whole guitar hero franchise. It is trying to take Guitar Heros place in our living room, but i don't think this will happen for a couple of reasons.
First, the price of rockband is too much. Plain and simple too expensive.
Second, where are you going to put all the crap (the drums especially). I takes up a lot of room that i walk in. The GH guitar easily stores next to the TV.
In the case of Rockband vs. Guitar Hero III, definitely, GUITAR HERO III. Why, because it is a gaming icon and can't be replaced but a cheap imitator.
