Old school days, my fave mmo was Ragnarok Online. It is simply beautiful and made a very good friend whom I met irl 8 years later from. It will always have a place in my heart. But steam fooked it up, don't play steam version it is rubbish! And RO2 is just not even worth looking at!
not as old school days: I rather enjoyed Aion, I played a cleric had a sweet guild thingy. But it went to pay 2 win very quickly, I never went back.
Current MMOrpg: Black Desert Online, played EU CBT and KR fully released version. Ah man, it has ruined me. I can never look at another mmorpg the same, because of the in depth character creation tool, simply magnificent.