I dunno though, the music game scene in Japan has been around since the 90s and is still pretty consistent. The releases are much more spread out, and genre decay still really hasn't take effect despite only minor improvements made with each new installment.
Spread out? I'm sorry, Beatmania IIDX is on its 17th release on the PS2.
The problem with Guitar Hero last year is that after World Tour, Metallica was a small step up, but Van Halen and Smash Hits did absolutely NOTHING, so it was boring as fuck to play. No improvements, same UI, same base characters and shit.
GH5/BH was perfect, but they didn't need both. They just did way too much. When I GET people to try GH5 they're amazed, but by this point, they just assume it's all the same.