Of singleplayer games, it may be Quake. This one was created before the recent remaster and compatible with different engines.
In honor of Quake’s 20th anniversary, MachineGames, an internal development studio of ZeniMax Media, who are the current owners of the Quake IP, released online a new expansion pack for free, called Episode 5: Dimension of the Past.
I wonder what is the oldest game to get a real expansion.
Of singleplayer games, it may be Quake. This one was created before the recent remaster and compatible with different engines.