My problem isn't the way things looked but more or less how playable the game is. Try playing bond on the N64 multiplayer or Perfect Dark. Watch that frame rate drop to single digits. Some old games are hard to play because we are now use to a minimum of 25-30 frames per second and that seems very smooth.

The other problem I have with some older games is that gameplay mechanics have improved that much. Try playing Syphon Filter on the PSX and you will see what I mean. The way the 3rd person shooter has evolved has gotten to the point where early games like Syphon Filter or Tomb Raider(to some extent) have become hard as hell if for no other reason than we can't do what has become standard.

I still play old games on all systems going back to the Atari 2600 from time to time (Koolaid man RULES!) but I do avoid some like the plague not because they look bad but because I now view them as practically unplayable.