I've been taking a look a the post-SA2 3D Sonics and god. I mean, GOD.
I remember playing the demo for Heroes when I decided to back away. Shadow as a guaranteed no-purchase, but jesus christ what were they thinking. I just wanted to see what the last level was, so I looked it up on Youtube and instead found a 6 minute cutscene from before the final boss.
Then I wanted to see stuff from Sonic 06, and was treated to a bunch of different characters with crappy control styles and lots of emphasis on beating up enemies before continuing.
Secret Rings obviously has its share of problems, but Black Knight is Shadow-levels of bad. And Unleashed doesn't look terrible, but it does have a number of things that looked like they would annoy me, namely the werehog, seemingly abundant cutscenes, a fucking hub world that would make me want to stab things (why would they bring that back from Sonic 06??). The (daytime) levels look beautiful, but with no emphasis on exploration or platforming. They appear to be pretty automatic (for the people).
Back to Sonic Colors, the only things that would really impress me is if every Act in Sonic Colors is an actual level with no special objectives, and if some Acts are unlocked by finding secret exits. A Sonic game being good (meaning music, design, story or lack of it) shouldn't be impressive on its own, but it is at least reassuring.