All the major MMOs I've spent too much time on, in order:
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Phantasy Star Online
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Maple Story
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Guild Wars
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World of Warcraft
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Guild Wars 2
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Final Fantasy 14
Met my first girlfriend through Maple Story.
Guild Wars 1 is ultimately one of my favorite games of all time, and it's a crying shame that no other games have taken its approach to skills/attributes.
WoW was my first foray into mass event organization and being a sweaty tryhard. TBH playing WoW is what gave me the skills to get through my uni degree.
Guild Wars 2 is a huge disappointment and I cannot recommend it to anyone. You're better off playing FF14.
There's only a narrow range of content worth experiencing in FF14, and it's all the single-player story from the last two expansions.