Of the players mentioned, Green is the best of the bunch at this current moment. I'll take Drummond first simply because he is still so far away from coming close to his ceiling - his combination of size, strength, and athleticism is rare. Kaminsky is pretty clearly last, IMO, though I wouldn't be surprised if he turned out to be a good player.
The Towns/Okafor question is a bit tougher. Towns is the more polished player and certainly a better bet to become a dominant two-way force, but Okafor is the best post scorer since who, Duncan? Not comparing the two, but Okafor scored more "that was way too easy" baskets than anybody I can remember. There are red flags with him though. He isn't an especially good rebounder for his position and he doesn't have the defensive instincts Towns does. I also think he's a bit overrated as a playmaker and I wonder if his bully-ball will translate to the pros as well as it did the college game.
If I had to list them I'd go Drummond, Towns, Green, Okafor, Kaminsky
