If you want to beat WoW this is how you do it.
First of you build a very good story line, make sure your able to edit it without making space paladins.
Then you create the world, lots of detail, lots of interactive elements and nice graphics, not crysis like.
Then you choose the classes, too many and it gets complicated, too little and it gets boring, make them unique and watch class balance closely.
Then you turn it into a FPS, making it a FPSMMORPG with 3rd party option, add physics, add interact able physics elements e.g. boulders blocking doors making them unable to be opened etc.
Then you try your hardest to hold onto the original development team otherwise you loose the plot and make space paladins.
Then you market it well and make it nice and cheap to buy and monthly sub.
Your done, you'll have a winner.