D4 could be the best Diablo game if they bring back D2 features and additional innovations. After Diablo 3 fail (even though they sell millions of copies), this is the last chance for Diablo series. If they screw again, i will never give a chance to any new diablo game for sure.
D1 is a breakthrough, D2 is a legendary game. D3 sucks. Please D4 be a good game. And make Diablo series great again.