Activision has disbanded it's Guitar Hero publishing unit due to declining interest in the music game genre. Undoubtedly the multiple versions of the already over saturated market of music games had something to do with this.
I first played Guitar Hero back on my old PS2 way back in... oh... I think it was 2006? Or was it 2007? Who knows. It was a few years ago. When I first strapped on my little guitar, I knew there was something special happening. I was immediately immersed into guitar karaoke at it's best. Since then, numerous titles have hit the market, but none others ever reached the brand recognition of Guitar Hero (although Rock Band came close).
Rest in Peace, Guitar Hero. We had some good times. Thank God they've finally decided to stop beating the dead horse.