THIS IS WHAT 3D SONIC SHOULD FEEL LIKE. The biggest problem I have with most 3d sonic games is that there's no sense of momentum. In the classic 2d games you had to build up your speed as you make your way through the level; you had to EARN it, and that's what made those games so satisfying. In most modern 3d Sonic games, you can just press a button and immediately reach top speed, which makes it feel cheap. But Sonic Utopia brings back that sense of momentum that has been absent in Sonic games for a long time. It's both amazing and sad that a free fan-made tech demo is more fun to play than a large majority of triple-a games.
However, I do have some criticisms. The game feels a bit too floaty. When you fall, you fall at a constant speed like a balloon. It would be better if Sonic picked up speed as he fell. This lack of downward acceleration makes smaller jumps very difficult because you always remain in the air longer than you expect.
Another thing is that Sonic is WAY too small. He should at least be as big as, if not bigger than the enemies. For reference, here's Sonic next to a badnick in Sonic The Hedgehog (1991) vs in Sonic Utopia
One more thing (and this is really nitpicking), I'm not a fan of Sonic's model in this game. I think it would look better if it was closer to his current design.
Despite these flaws, the game is an absolute blast to play. I give it a solid 4.5/5