One of my longtime favorite romhacks for keeping it simple. Sonic 1's weak points become a lot more manageable with the additional shields, Tails' flight, Knuckles' climbing and the insta-shield. And Sonic 2 is just as good as ever. Doesn't feel optimized for real hardware, though: Lots of slowdown in weird spots and a couple visual glitches.

Also, this hack made me realize 1's special stages are lowkey underrated