Actually CL existed long before 1999 -- I know that very well. I don't have an exact date; the 'official' release date was 1998, but it was just a rubber stamp thing; it had been functioning in Beta mode for several years before that.
The release date was just a question of resetting everyone's characters and starting again on a (must slower) experience path.
But there are still a few hundred players of Sierra's The Realm, which first came out in 1996.
There are also many community emulators for Ultima Online.
https://en.wikipedia.org/wiki/Habitat_(video_game)
https://en.wikipedia.org/wiki/Neverwinter_Nights_(1991_video...
https://en.wikipedia.org/wiki/Meridian_59
https://en.wikipedia.org/wiki/The_Realm_Online
https://en.wikipedia.org/wiki/Ultima_Online