This is widely considered the definitive way to play. It is a ground-up remake in the Unity engine by developer ChaosX that fixes physics, removes agonizing load times, and adds modern quality-of-life improvements while keeping the original assets.

Because the original developer, Sonic Team, was forced to release a build that was essentially an unpolished beta, the "fixed" keyword usually refers to one of three community-driven solutions:

If you are running the original ISO on authentic hardware or through an emulator like Xenia , you can "fix" many of the most glaring issues yourself: How Modders Fixed a Broken Sonic Game