Why is world of warcraft so successful?
alex_c: Short answer: you can't.Long answer:  some of the answers in this thread would in theory apply to any MMORPG, but the obvious reality is that most MMORPGs aren't huge successes like WoW.Some of my best guesses:
- great art direction.  All the locations, characters, monsters and weapons are colorful and unique.  Look at any screenshot and chances are you can tell at a glance WHERE in the game world it is - that's not true for many games out there.
- Blizzard has perfected an effort/reward system more finely tuned and addictive than that of any other company out there.  It started in Diablo and they perfected it in Diablo II - WoW is just a continuation.  Advancing is easier than in other games, but you know that the next reward is just around the corner so you play "just 5 more minutes".  In addition, the rewards somehow avoid being repetitive - it doesn't feel like you're just replacing a 5 with a 6 somewhere, like in other games.  As another poster mentioned, it's incredibly Pavlovian.
- Something for everyone.  WoW actually manages to be engaging for both casual and hardcore players, for two friends or a couple playing together and for a large clan who know each other from previous games.I don't think Blizzard put in any really innovative ideas in WoW, but their execution was far, far beyond what anyone else has done.  Of course, after all their previous hits, they also had the resources to pull it off.