I am a huge Sonic fan, and after all the fun Genesis games came out, I thought that they couldn't possibly get any better. I was wrong. The debut of 128 bits of graphics on the Sega Dreamcast was the greatest.
The action stages were amazing and I loved the fact that they had adventure fields, so I could run around and talk to people just for the hell of it. There were also different objectives for different characters in the action stages, which made it that much more interesting. Also, the story lines conflict with each other perfectly.
One huge drawback is Big the Cat. His story was awful. His missions included fishing for his friend, Froggy. The fishing was tough and not much fun. Another thing that bothered me a little was that every character (not including sonic) had only 5 action stages or less. They were fun as hell, but I wish that they were longer.
Overall, I recommend this game. If you don't have it, you are missing out on one of the greatest Sonic games ever to be made. I've gone through it five times and it's been loads of fun every time. I give it a 9.5/10 (Only reason it's not 10/10 is because of Big and the fishing)