Sonic Superstars is better than Sonic Mania.
In my opinion, Sonic Superstars is better than Sonic Mania because Sonic Mania has a big problem: recycling. Yeah, I know it introduces new mechanics to the levels, but there are only 4 new levels.
Then came the Encore DLC, which improved some things, but the Encore mode could have added new levels; instead, it just reused the levels that were already there. Plus, the levels in Sonic Superstars are more fun than those in Sonic Mania. I get that Sonic Mania is better in other aspects, like its soundtrack, but that doesn't change the fact that Sonic Superstars is better than Sonic Mania, at least in my opinion.