Rock Band. Like the fact that Harmonix has a full band practice area in their basement. That honestly just kind of makes us jealous. We are, however, intrigued by the possibility of including keyboards or (more importantly) cowbell to the set in sequels.
We're also happy to hear that the devs have based their World Tour Mode on the experiences of cool bands like Freezepop. We'd like to humbly suggest that other bands be consulted for sequels, like a "Sex Pistols" mode consisting of an hour of fun and three decades of coke-fueled irrelevance. And don't miss the "Def Leppard" mode, sure to be the one time no one's fighting to be the drummer.