I'd like to see someone make a multi-player one second per clock version of NetHack running from a central server somewhere. Or even use tiles instead of @ signs ala the early Ultima series.
for example the DOS games have a lot of potential for multiplayer gaming .. spectre VR over DOSEMU over IPX to a common pandora-fan VPN would mean we all could play on a local network of players ... is really feasible i think.