1. LeBron (Most complete player in the world, by a fairly wide margin)
2. Kevin Durant (Probably the league's most elite scorer, with only LeBron giving him a challenge, with an improving overall game, but still defensive issues)
3. Paul George (Strong overall game, with improving scoring [although still well short of Durant], and an elite defender)
I think George and Durant have similar all-around games. The difference between the two is that one's an elite scorer with adequate defense, whereas, the other's a very good scorer with elite defense. Right or wrong, scoring ability is largely considered a more valuable trait than defense (Dirk Nowitzki vs. Dikembe Mutombo, for example), so the masses will view Durant as the superior player. Also, Durant's been doing it for longer, so he's more proven than PG.
At this point, I consider George on a tier above Curry and Melo, a tier below Durant, and two tiers below LeBron. I think it's possible he could move up a tier to be on the same level of Durant, but moving up two tiers to LeBron's level is probably out of reach; LeBron's just too much of a physical freak.