Well, sincerelly, Sonic The Hedgehog is a sick concept, running trough levels at high speed, obtaining the emeralds, beating bosses, etc. it's kinda like every game is the same but with new gimmicks. After Sonic Unleashed, i trough the new gameplay style was good, so they made Colors, which was really vell received, Generations, which is still modded until today, and then nothing, they decided to make a sick mix of SMG and their old styles, it was preety terrible.
Again, they should start from the beggining, rethink WHAT THE F- is a Sonic game suposed to be, make something new, original and fun, but not getting very off the original formula, like they did in the last game, which anyway was a Spin-Off.