>>571
I liked S3&K's the most.
Sonic 2's special stages are fairly fun, but doing the last one with Sonic and Tails is a complete nightmare if you don't have a friend who is just as good as you to help.
Sonic 1's are a neat idea, they're just not great.
CD's look the coolest, but I remember the later stages being a pain.
Chaotix has the absolute coolest special stages to the point where I'm actually convinced they spent more time on them vs the actual game, but I'm terrible at them and have never gotten all the Chaos Rings. so I refuse to say they're the best. You also move a bit too slowly, or maybe the camera FOV is just set up that you don't get a good sense of speed.