Kyrie Irving no doubt. He's a superstar now and will only get better.
John Wall to me is still a "remains to be seen" but I put him second. If Wall can consistently hit jumpers, he can be a much better player than Irving (yes I said it). He's WAY more athletic compare to the two. His court vision I think is also better than both. With his physical gifts and maybe the right situation and coaching, he can be a lockdown defender, I don't see Lillard and Irving being one (not saying they are bad defenders) so my judgment on John Wall is still out. But Irving is miles ahead of him at the moment.
Damian Lillard is a multiple All Star player, but I think Wall is better, by a bit.