Originally Posted by Mega Man
WoW also has a huge community of add-on makers, and many of them can be used to really customize the UI, and overall look of the game. Even better, it doesn't breach the EULA, and there are a handful of really useful add-ons.
The other thing that makes WoW appealing is how the quests and leveling flow together. You can easily do quest after quest, each leading you into a chain or a new area where the enemies are around your level. Other MMO's I've played I felt more lost, whereas WoW really tells you where to go for your level.
There is a problem however with WoW's community (as with most Blizzard games). There's really some elitist nazis in there; who aren't afraid to call you out on anything you do wrong (or if it just differs from their opinion). Try playing any of the RTS games and being a noob. You'll get cursed at pretty bad.
Wow really did make their questing system right. I remember playing Everquest and as a noob you should be completely lost. Before later expansions, I remember it being a adventure to just find your way out of town. After a while, knowing what to do made the game fun though. I wasn't a real big fan of FFXI and never got past level 16-18 (I remember spending 6 hours getting a chocobo license). Never figured out how to do chain attacks or burst with my friends either.