Alright, I gotta say, I just tried out Sonic Advance 1 and 2 on GBA emulated on my PSP, and I'm really surprised. It still has the goofy art style and animation a little reminiscent of Rush and Sonic 4. But the physics weren't extremely wonky, and the walking/running animation flowed better with the movement, so it didn't look like he's floating/gliding on the ground like in Sonic 4. The physics worked with the speed. No sudden stops in loop-de-loops, or pulling out of spins and randomly going into a run on a downhill like in Sonic 4. So really a new Sonic team has actually done it fairly right at least once since Sonic & Knuckles. I'm both impressed and saddened that I only just now realized. But Sonic Rush and Sonic 4 both still blow in these regards. And I watched the GameTrailers review of Sonic Colors for DS that says its just like Sonic Rush but with weird alien powers and abilities. Nice idea. But that whole physics issue and floatiness drive me crazy. Not to mention the version of Rush I have has all these crazy death traps so you don't even want to go fast. Egh..
But thankfully there's some decent Homebrew projects out there