The elephant in the room in this comparison is that Durant is frail and Lebron and Melo are built much like a Power Forward. Durant NEEDS refs to call a foul when he is driving in the lane or needs the court to be spread out. He can't be physical and get a tough shot like Lebron or Melo. On the other side, he can't play physical defense, either.
Durant can be the 2nd best player in the league statistically if he is on a good team but he needs a 2nd superstar more than Lebron or Melo.