For sheer skill, I think Sugar Ray Leonard would be on most people's list. He wasn't a bad puncher either. He belongs on another list with Sol's best "pound for pund" fighters though.
Lennox Lewis's foolishnes, in failing to train properly for two of his bouts, meant that he lost his unbeaten record. However, when he finally retired, he had beaten every man, who had ever entered the ring with him. Both of his rematches were mismatches. He also improved as a finisher in the course of his career. I would have to look at footage of the fights to decide whether he or Larry Holmes had the better jab. It would take some figuring out even then. I would not fancy a clout round the ear from either of them.