As an example back around April a company called World Inc. started suing major video game companies like Blizzard, regarding patents 8,082,501, 7,493,558, 7,945,856 and 7,181,690 "System and Method for Enabling Users to Interact in a Virtual Space".(original filing, November 1995).
Virtual reality systems to the best of my knowledge were being developed and tested before November 1995(see the guys at VRML - April 1995, but started work in 1994) not to mention many games, although while primitive also used various aspects of what they are claiming. See CitySpace (1993,1994 - SIGGRAPH), various Text Based (MUDS), Wolfenstein 3D(July 1995), Worlds Away(September 1995), Habitat(1986, 1988, 1990, 1994), Neverwinter Nights(1991)
To my eyes their patent claim describes pretty much any 3D multiplayer computer game in which the game is hosted by a central server.