Asheron's Call in 1999 was my first online gaming experience - also my introduction to MMORPG's. I played that game off and on for 5 years. But realized what a colossal time sink MMORPG's are so I stay away from them now. Also played Unreal Tournament in 1999.
I'm not that big of an online game fan. Guess I've run into too many "doods" over the years and it's turned me off to it a bit. Every once in a while I'll jump in - L4D2 for example - but more often than not, I prefer playing standalone games. Games like Bioshock, Crysis, Mass Effect series, Dragon Age, etc. I love those kinds of stand alone games. No expectations from other players, don't have to deal with jerks or cheaters - just play at my own pace and enjoy the story.