User blog comment:Shan the Hedgehog/Level List, A Few Characters, Bosses, DLC, And More Confirmed For Sonic Generations/@comment-1945883-20110624154727/@comment-477304-20110624164945

For the 3DS they're adding handheld levels as well, it's not just the three levels and handhelds from what I gathered, but that means potential levels from the 8-bit versions of Sonic 1 and 2, including Sonic Chaos, Sonic Triple Trouble. As well as more recent ones like the advanced, rush and rivals series. So doing handhelds will give them a wide variety of levels to pick from