Unfortunately, games that truly exploit the 3D aspect in their stage design are often difficult if not impossible to properly represent on a 2D map.
And even if you somehow manage it, you only do so through a lot of compromise. You have to do things like schematize or show multiple views of the same area. In short, you simply cannot communicate all the intricacies and all the beauty of a stage in a single instance the way you can with most 2D games.
Take Metroid Prime for example. That game has gorgeous stages with wide open spaces full of life, lots of corridors and cramped rooms, secret tunnels with puzzles for the Morph Ball, etc. You can't show all this to anyone unless you play the game in front of them. You can't do an awesome collage showing all the various areas in the games put together the way mappers have done for all the 2D Metroid games. Sometimes, I feel the only way to do it would be to extract all the game's level data, 3D models and all, find a way to then render the level with items, enemies and everything on the computer from whatever angle you want, with transparencies being used whenever a part of the map hides another. And even if someone managed to accomplish such a monumental task (unless he worked for Retro on said game), I'm pretty sure it would be impossible to find an angle from which you could see an entire area without hiding something somewhere or making a room's structure somewhere hard to make out. And that sucks!
Oh yeah, and I remember Descent (I only played the first one). It had a great automap that you could rotate in every direction, and unfortunately it was absolutely required to do so because many levels had nightmarish structures and it was incredibly easy to get lost somewhere because you didn't recognize a certain room simply by not being oriented the same way when revisiting it.
---
Current projects: Metal Storm (NES), Clock Tower (SNES), Ristar-The Shooting Star (Gen), Sonic The Hedgehog (Gen), Sonic CD (Sega CD), Mega Man Zero (GBA), Battletoads (NES), Bucky O'Hare (NES)
