Ok, been playing Sonic Generations on Xbox 360 (I got the big collector's edition. Europe and Australia only they said and thank god I'm an Aussie).
Anyway, I actually liked this game (considering the last Sonic game I liked was Sonic 06 and that was only cause of Shadow n Silver's levels - Sonic's were just shit) and think they may have got modern Sonic to the level that's enjoyable to play. I also like the fact that the camera didn't screw you over when you play. Game play is good and the controls are easy enough to use.
Music is just what you expect from Sonic games these days (though this one lacks modern theme, using the classic one instead). The cut-scenes are also well done. Story wise is fairly simple and predictable.
The real fun is experiencing those classic levels from different perspectives as each one has been designed for Classic Sonic and his classic 2D game play style and one for Modern Sonic and his 3D style game play. Rivals and Bosses are designed only for their Sonic's (So Classic ones are classic Sonic only, Modern ones for Modern Sonic) with 3 Rivals, 3 Bosses and a Final Boss. I'm still trying to figure out which Final Boss was the worst, this one or the Sonic Unleashed one? Still, I enjoyed this game overall. If you want a good Sonic experience, at least give this one a shot.