Polish MUD "Well of Souls" in 90's. I had almost failed my exams because of that, but on other hand I met many great people there.

Can't say I really remember, but I think that I didn't get deeply into anything online before UT2003.

Warcraft II in dos connected over a modem with a friend (no actual internet connection at that point). Then Descent. Once I got an internet connection, Tribes.

I played Duke Nukem 3D cooperatively via modem with a friend once. I found that I really did not play these games like everyone else. I'm slow and methodical, I had to run after him in order to kill one monster from time to time.

I played Nascar (The last DOS one) on lan with several players a few time but I was not very good. Same thing with RTS, I play to defensively to last long against aggressive human players.

I played one game on Yahoo against a stranger. I think it was backgammon, I was dismayed that he wanted to chat while playing.

In the end I prefer playing alone against the computer. It's always there and it does not mind if I take a break.

Aside from my Commodore 64, most of my gaming experience has been on consoles. The one exception was the original Diablo. While not my first online interaction, it was my first online gaming interaction. Coming into contact with different types of people like hackers/cheaters, player-killers, campers and looters made for a very interesting, and eye-opening, experience.