Completely agree that its very difficult to rank across era's. Of those 15
Manning - obviously great but not #2 for me.
Favre - too wild to be that high.
Young - excellent and a threat on the ground but somehow he doesn't feel like a top 10 of all time.
Mahomes - is the best blend of all the traits we have ever seen. could very well challenge for top spot by the time he's done.
Elway - Way too low. Was the prototypical size with great mobility and a cannon for an arm. Tremendous competitor. Found ways to win. He truly changed the game.
Warner - Nice to see him get the recognition he deserves. An absolute surgeon. His career cut short by late arrival and some injuries prevented him from having a long run of sustained play but when healthy .... awesome to watch.
Question I ask myself is who would I most want to play the biggest games against the best competition. In no particular order, Mahomes, Rodgers, Elway, Marino, Brady, Montana & Warner. Give me any of those guys and I feel really good they will come out on top.