Aquarium Park from Colors, City Escape from Generations (I prefer the redone version), Volcano Valley from Sonic 3D Blast is also a personal favorite. There was somebody online who did a "generations remix" of both acts of Volcano Valley and it's phenomenal.
There are a bunch.
You should check out my YouTube channel, The Golden Bolt! I review all types of video games, both classic and modern, and I also give short flyover reviews of the free games each month on PlayStation Plus to tell you if they're worth downloading. After all, the games may be free, but your time is valuable!