I played through Mega Man X recently with my cousin via my PowerPak, and we've now moved on to X2. Since it isn't supported by the flash cart I turned to my Gamecube + SD launcher for emulation.
Going from the SNES to the GC, there's a marked improvement in video quality. No vertical line, no shimmering color, just a very solid and sharp image. And I've played on all kinds of displays through nearly every kind of video standard available, including RGB and pro monitors.
Playing SNES games through the GC looked, well, good. I really have a hard time finding major faults with the image. Perhaps s-video or component could make the colors pop a little more or seem more contrasty, but I don't think there's any loss of detail. Granted, this is coming from a fairly run-of-the-mill CRT TV.
Genesis games benefited even more. Given how some games took advantage of certain aspects of composite video, this might be one of the best ways to play them.
Now if only I could find a proper button mapping...