Leo and Armie Hammer

'But for my money, Hammer had the edge. The tragedy of Leo is that he is always good but his co-stars are better.'

Sorry to disagree but I don't see it that way at all.
The only real time that one of Leo's co stars seemed better than him was in Gangs of New York. But even then its misleading since DDL character was meant to be the dominating character. You can see that from the script.
When you have a character dressed like that with the top hat and tails, called the Butcher,one who is built up by other characters as this deadly force and who is handed scene's such as the one where he is wrapped in the American Flag, has the five points of New York dissolve into the palm of his hand as he intones how he rules the place, and the scene where he uses the Butchers knife to show Leo how to kill a man, etc, then its no surprise that the actor playing this character dominates the screen.
Especially since DDL hams it up while Leo plays down his own character. leo is the scrappy pup while DDL character is the Junkyard dog. Daniel Day Lewis is a GREAT actor, but he had that movie handed to him on a plate.
DiCaprio has never been bettered by any actor he has been up against. He cares about the overall movie, not one upmanship. In fact, in this movie it is clear that he is the one doing the heavy lifting. Hammer is reacting off him, feeding off DiCaprio's performance. Any actor knows your only as good as the actor your playing opposite. And while Leo is consistently great, a lot of the actors who he plays opposite are never as good in there other movies.