Top three, eh? Hard question for anybody who has been playing for 20+ years - those early games are getting the nostalgia bonus yet can’t really hold a candle to modern games in many ways. After a lot of thinking, I’d go with
#1 World of Warcraft
Yeah, it’s a popular target to hate these days, and I’m not playing it any more, but it still is a yardstick for me for many things. And I played a hell of a lot of it, too. I’d still log on from time to time if it was free, but I’m not going to sub to it just to look around.
#2 Angband (and its variants)
Adding all the variants together may be cheating, but they are all branches of the same tree. I first played Moria around 1990 (give or take a year or two) and then switched to Angband when that came out. ZAngband, OAngband, SAngband … I’ve sunk endless hours into them and I still sometimes do, despite how old they are and how slowly they progress these days. Played quite a bit of ToME as the first thing on this new computer a few months back, and that’s a distant relative of the Angbands as well.
My first MMO love. You can’t relive the first and best honeymoon again, though WoW came very close. I played an inhumane amount of it back in the day, when my RL was shit and I really needed a way to escape. I was truly an addict, but thinking back I also feel that it helped me get over all the shit. Who knows how it would’ve gone otherwise. A lot of boring grind, downtime, waiting, trying to get a group - but time has faded all those memories and left only the good stuff, the legends, the feeling of discovery and making friends and exploring deadly caves that held actual peril. Breaking into fully spawned Planes of Hate or Fear, getting horribly wiped by the old world dragons, drama over loot … you had to be there. Today, I can’t bear to play EQ1 - the UI is horrid and the controls and graphics seriously outdated. But those stories, man … those I will carry to my grave.
So that’s WoW as the newest, launched in 2004.