I have a feeling that some guys here tend to overrate Melo because the Knicks are playing very well at the moment. As far as I know he hasn't achieved that much yet. And let's not forget that Melo takes a ton of shots every night! Lebron on the other hand plays more like a facilitator. So it's hard to compare these two guys.
Overall I'd still give it to Kobe. He's been a scoring machine for many many years. Durant has been the best scorer for the last 3 years, so Melo would be nr. 3 on this list although Lebron probably could be a better scorer than Melo if he wanted to be!