I rarely post in this forum, or any for that matter, but on this I have to disagree. Having played World of Warcraft since the month of it's release, and also having played, EQ, EQ2, City of Heroes and Villians, D&D Online, Ragnarok, Lord of the Rings Online, FlyFF, Fiesta, Maple Story and Dream of Mirror Online, I can safely say NONE, not ONE of those games comes even remotely close to being as good as WoW.
While EQ2 is an amazing game, the fact that you can run through zone after zone and not see one other player kills it. There is no socialization at all. Why? The sheer lack of players.
City of Heroes/Villians is also amazing for it's own reasons, but running the same missions over and over again gets boring, quickly.
D&D Online was just a big joke. Same with LOTRO.
FlyFF, MapleStory, Fiesta, and Dream of Mirror don't even compare. They are all fun, and cool, you get to whack little mushrooms in the head, but seriously? With the insane amount of lvls in these games, and games like it, how is this fun? Grinding and grinding for hours on end, and for what? So you and the 2 other players with enough time to reach lvl 3,573 can stand around and look oh so cool in your Cosmic Armor or something. *Edit* Also, none of these games are actually FREE to play. They all have a cash shop, and to get anywhere in the game, you need to spend all the money you can in it.
WoW is popular because it targets lots of people. Casuals, Hardcore players, PvPers, and just about everything in between.
Also, did I mention that almost ever single one of the games I have mentioned has tons and tons of loading screens. Between every zone and city. WoW has very few.
Should I also mention how much it actually cost to MAKE World of Warcraft?