NES, SNES, GBA and GBC games don't really need upscaling because of their 2D pixel art style (although we did see Nintendo try its hand with a CRT filter on the NES Classic).
I wonder if GCN games will look too blurry though, if not properly upscaled. It shouldn't be too much for the Switch to deal with, given how easily modern emulators do the trick.
What do you guys think?
Discussion started at here by bizarro_kvothe