I think it's a combination. The game has to be balanced. There shouldn't be one class that is overpowered. There has to be a wide variety of items and the gameplay should be as easy as is it now.
But nothing beats an extremely cool "feeling" when playing the game. But to get that feeling the game needs a lot of things and it need to be as addicting as D2.
I think you should change the question and ask "Which aspect of D3 do you think is least important" and you'd get better answers.
Stuff like music is something I think most can live without. I always turn that stuff off anyway. Also I never liked PvP in any game really. D2 pvp was only fun when you could make people drop all their items on the ground when picking up their bodies.
