Most console games end up having textures high res enough to look better than the original hardware if you render them at a higher internal resolution. There are some Wii and Wii U games that look spectacular if rendered at higher res, and the same applies to Switch.

If you emulate on fast enough hardware, for games that emulate well you will hit whatever the game's framerate cap is (sometimes 30, sometimes 60) flawlessly where the native hardware struggles.