Speed is considered the key trait of Sonic’s gameplay. The thrill of blazing through landscapes and the challenge to quickly complete stages is almost always a selling point for his games. This past decade, his speed has been amped up even further, most notably by the recurring Boost mechanic. You’d think this would cause the thrilling appeal of his games to skyrocket, but his general reputation says otherwise. It’s no secret that most of Sonic’s newer games are received less well than his older games (with the rare nostalgia-heavy exception). When comparing these games against each other, one common topic of praise or criticism recurrently appears without fail: the physics.
This isn't a big surprise. Sonic's a platformer, how he moves affects whether the game is good or bad. But this topic still comes up much more often in conversation than it does for most mascot platformers. Sonic, however, isn’t a usual platformer. His games are driven by platforming across stages as speedily as possible, and as such, the methods by which players manage their speed acts as the cornerstone to that experience. So, what defines good physics for a Sonic game?
via destructoid https://www.destructoid.com/why-physics-matter-so-much-to-sonic-games-487440.phtml