There's a core on Retroarch called "Genesis Plus GX Wide" which as far as I can tell, seems to support true widescreen. That's what I was referring to. But yeah, it would require quite a bit of work to hack a rom into taking advantage of it. Give it time though.Well, for emulators it would require much more work and you won't have the smooth rotations not advanced stuff. I don't recall any emulator supporting true widescreen as far as I can.
EDIT: Oh hey, someone already made a widescreen patch for Sonic 1 and 2 for it. It's called heyjoeway's widescreen patch. Cool.