I don't know what we have for real time rescaling but if you have the PC version then I am sure you could downgrade the textures and then maybe render things at a lower resolution, possibly even interlaced PAL and NTSC low. The same stuff that helps people do widescreen and such like for games that do not take it might also help you here, http://www.wsgf.org/mgl
being a good jumping off point there.
If you are good you might even be able to chain it with a CRT emulation filter http://bogost.com/games/a_television_simulator/
If you would rather go hardware then it is possible -- I do have a VGA downscaler around here somewhere aimed at early plasma screens and that might do well for such a thing if software is not an option. As nobody should want one any more you can probably pick one up for not a lot.
Whether you would want to go all the way and reduce draw distances and add fog is a different matter, a lot of games of the time had their levels designed for it though (go back and play mario kart 64 and watch for the track design that sees you have a limited visual range) where later stuff was quite the opposite.
On consoles it is a bit harder, however the same thing that sees people do texture mods for games would also do for what you want.