It’s big. Oh god, it’s big.
World of Warcraft is the world’s most successful subscription MMO. Orcs and humans, fighting dragons. It’s four games welded into one vast whole: a multiplayer cooperative RPG in which you quest. A competitive fantasy team battleground game. A three-versus-three arena competitive ladder. And a 10- or 25-man dragon bashing cooperative raiding thing.
Together, those elements make for a deep and terrifyingly compulsive mix. The trouble was that to get anywhere in the latter three games, you had to go through the former.