To be more specific about the colors... and this is especially true with that gradient bullshit... the SNES has a 5/5/5 RGB scheme, whereas the Turbo and Genesis both have a 3/3/3 RGB color scheme. The extra bits available to the SNES give it a lot more flexibility, and some games took advantage with all the sickening gradients. Remapping colors for the PC from the SNES isn't difficult though... quite often, it's just a matter of slightly raising or lowering individual palette entries to fit into the approximated colorspace for the PCE (offsets of 36.43 in 24 bit colorspace). Screenshots from SNES emulators seem to always have colors with an offset of 16 or 17 in the 24 bit colorspace, and rarely do SNES games use shades that are so close together than remapping produces identical color results. You really only start to notice it when dealing with, again, those nasty gradients... but then, you can also "cheat" a bit there and use dithering between the bands to achieve similar results.
Example: say one color in the SNES palette comes out to be 33,66,99 in 24 bit colorspace (16+17 = 33, then multiply). The 33 is raised to 36, the 66 is raised to 72, and the 99 is raised to 108 or 109 (depending on how strict you want to be). In some cases, depending on how it looks, you might actually lower a color rather than raising it; it's not usually the case, but it does sometimes look better that way. In any event, this is something you generally want to do manually rather than letting an automated tool do the work since eyeballing the end result is of critical importance.
