I have a similar question. I though I'd post it here instead of opening a new thread.
How is Wii displaying Virtual Console games? I know that for N64 it upscales them to its own resolution and they look quite better than N64 itself. What about SNES? I recently downloaded Final Fantasy VI and it looks absolutely terrible. I think it doesn't upscale the resolution at all, but I can't confirm it anywhere. Can anyone clear this out?
The SNES, like the N64, had a wide variety of internal resolutions it could render at. It then would be scaled to 480i for the output.
Take Ocarina of Time. The actual cartridge itself rendered the game at 320 x 240 pixels, which was then (I assume) sent to the scalar and converted to 480i. But, if you play OOT on an emulator, you can render it internally at 1080p or even 4K. The main advantage of this is that if you plug a N64 into a 4K TV, due to the stretching of the vector graphics, lines will look very jagged, whereas an emulator will render polygons at the native resolution of the TV.
The gamecube version (which is what they use on the virtual console) has taken a similar path and renders OOT at 480p.
So, if you look at the older systems, like the SNES, realize that their internal rendering can be a full 480, or half of that depending on the game.
Since SNES and NES games were mostly non-vector graphics, having the emulator render the game at a higher resolution is not as advantageous as for 3D games in the following eras.
To make matters worse, the 480 output is upscaled by your television, and unless you have a CRT (which can actually natively draw pretty much whatever resolution it wants by controlling how the electron-gun fires), there is some digital stretching going on.
On my Samsung plasma, Wii games often look very bad. There seems to be some artificating from the upscaling that looks like old-fashioned interlace lines. One possible way around this is to get a component to HDMI converter that can do a better job at the upscaling.