>>77I'm interested in how Sonic Xtreme would have turned out, because I'm not so sure Sonic was supposed to die with the Genesis. He was a very successful mascot and had more games planned, but the war between Sega Japan and Sega America killed that game. The entire Saturn era of Sega is just sad.
Personally, I think puzzle elements should more or less be removed entirely. 3D Sonic is at its best when it feels like a rollercoaster ride, with the challenge being centered around effectively navigating the environments without losing speed and chaining up combos by killing enemies, which usually leads to secret paths.
I think the multiple "branches" through levels that the Genesis Sonics had, combined with their emphasis on maintaining momentum, could even be considered the core of Sonic design; if a 3D game were to focus solely on these elements and design the entire game around them in various ways, I think it would be a very compelling experience.
The problems with 3D Sonic have been trying to incorporate elements of other contemporary 3D platformers, such as the adventuring and exploration segments in the Adventure games. These should be done away with entirely to create a mostly linear game with branching paths, where which path you take depends on how well you're able to maintain your speed (keep up enough momentum and you can reach the classic "upper path" like in most Sonic 2 levels). Certain branches could lead to different zones, giving the game a lot of replay value since you wouldn't be able to see every level on one playthrough. And the game shouldn't take more than 4-6 hours to complete; Sonic's biggest strength was speed and replay value.
That's how I would try and "fix" Sonic, at least.