The first heavyweight champ against the greatest heavyweight champ ever, who wins? I think Louis would score a late TKO.

I concur, as long as Louis is fighting with gloves.Bare Knuckle, it's Sullivan's fight.

The first heavyweight champ against the greatest heavyweight champ ever, who wins?

In response to this Ali would stop him on cuts late, but in terms of the thread Louis kos Sullivan in 9 rounds.:D

I think this would be like Louis vs Galento. JLS would be dangerous if he connected. But, my bet would be that Louis gets to him first, quickest, hardest, most often and last.
Joe Louis by mid round KO.