I my opinion, you should try out a system similar to what ElderScrolls Oblivion or old Runescape used and make it mostly 'First Person' POV. It may be more difficult to code but would prove more 'fun' in the end. I've tried games like WOW and EVE but I grew tired of them very quickly, mostly because of the combat systems that didn't involve much of the players skills. I especially like Oblivion because the player has to actively hack and slash through opponents rather than just 'point, click, fight'. Another thing, stay away from elves/dwarfs/orcs/trolls/gnomes ect. They have been done to DEATH. Nearly every fantasy MMO I've seen has them in one form or another. Break out of the mold, be creative, player characters don't always have to be Humanoid, either. Best of all; make it something you'll want to play as well.

Also, make dragons a playable species!