Everquest was my first MMO, I was 11 years old I think. I don't know how old you all were when you first got started but being 11 and playing a classic MMO like Everquest was, slightly confusing, but mostly- EPIC. It was the first MMO I had ever experienced and I was amazed at the technology alone. Being online with thousands of others was unheard of for me. I didn't really progress very far though, I was 11 years old and 15 bucks a month was to steep for me at the time. I went on to try out Asheron's Call 1 and 2, played Shadowbane, Earth and Beyond- I've played them all. Not for great lengths of time but it's a hobby to at least give most MMOs a try. I mean really, the list seems endless. EQ2, Guild Wars (if that counts), PotBS, FFXI and XIV, Aion, Warhammer, AoC, LotrO, Fallen Earth, many more, countless Free2Plays- in other words, I've spent way too much money on MMOs. Most of these games I didn't get past the free month though.
Truthfully the only MMO I've ever found myself fully engaged in was/is World of Warcraft. I haven't played for a few months but I fully intend on going back when the expansion drops next month.