Something magical happens when a game's sequel is released only a few months after the original: they tend to look exactly the same. When those games are part of a franchise that pretty much always looks the same (look, there are guitars and dudes playing them; what more do you want?), then, well ... you really can't expect anything different.
There are legwarmers to sign, though. And platform shoes. That's how you tell the decades apart. Genius. Guitar Hero: On Tour Decades is set for release before the end of the year.