My favourite 2D Sonic.

I have some minor annoyances (nitpicks really, I don't even think they're worth mentioning), but nothing that kept me from enjoying the game.
Everything felt intuitive, the special stages are playable, the setpieces are memorable, and the game doesn't punish you for going fast.

Oh also, switching between controlling Sonic and Tails at anytime during the stage is fantastic.
Missed a jump? Just switch and fly back up (because there's not gonna be a bottomless pit! Unless it's one of like two instances where you're hanging onto the side of a moving vehicle.)