This unofficial project ports back most of Sonic Unleashed's day levels from the Xbox 360 version into Sonic Generations on PC. It also includes any improvements that are deemed as necessary to accomodate to the better control scheme, higher resolution graphics, and a much smoother framerate.

MysticHyperSonic says

10/10 - Agree Disagree

No console limitations. This means support for unlimited resolutions, high-quality texture filtering and 60 FPS gameplay as long as you have the hardware for it. Stages that had performance problems in the original game now work perfectly (with a proper setup).
Eight Modern Sonic stages completely readapted from Sonic Unleashed. Lots of layout improvements, recreation of gimmicks, and fixing various bugs/glitches.
Brand new White World Stage for level selection. Enjoy the new soundtrack arranged by Falk.
Various High-Definition retextures by Lobotomy.
No mandatory RPG elements, no medal collection, no Werehog.
Superior control scheme, player speed, consistent camera control (no wildly changing FOVs or distances that would make a player nauseous and confused), support for various skills (such as Super Sonic), etc.
Classic linear progression system for starting a new game. This new game won't overwrite your current save file (as long as you don't disable savefile redirection), so you can collect Red Rings and have new score and time records.
New Red Ring locations for each level. S Ranks will require you to speedrun and optimize your route as much as possible.
Alternate and experimental FxPipeline renderer included within the game. Provides support for special effects from Sonic Unleashed, such as directional shadows, directional light shafts, better motion blur, and much more! (Recommended to use)