World of Warcraft
This game is probably the closest thing you are going to find to the holy grail of mmogs. It is the Half Life 2 of MMORPGS (I repeat OF mmorpgs, nothing comes close to Half Life 2 in its own arena). If WoW has one fault it may be its player vs player and player vs enviorment balancing issues, but no mmorpg is going to come close to what this game already has in those terms.
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