I started playing MMOs when they were called Graphical MUDs and players were called mudder's. My first ever online MMO type game was Ultima Online, just after it launched. From there I beta tested several MMOs including Asheron's Call and 4th Coming. I eventually played Asheron's Call until I was told about a little known SOE game called Vanguard: Saga of Heroes, which is the best ever MMORPG I have ever been involved with. Sadly, SOE treats it as a red headed step child so to speak (nothing against red heads) and keeps VG out of sight/out of mind.
I'm not sure how many MMO years its been. definitely 15 plus and counting.