They were great for that time but Heavyweights got bigger and stronger. But that doesn't mean anything they were still the best of there era even if you question there opposition you can't deny they fought everyone. And i think your forgetting Marciano would be in Cruiserweight division now which i think he would very well in. And lets not forget imagine if Marciano, Louis, were trained like modern fighters they would be even better. And i for 100 percent would give a prime Louis a shot against Ali in the 60s. Louis had such devastating power on the inside with his short little chopping hooks, there is a reason he is called one of the best punchers of all time and ditto for Marciano. Louis also had great hand speed sure he was flat footed but that doesn't mean he hasn't got a chance against Holmes, Ali, or Foreman. Because both Holmes and Ali have struggled with fighters who didn't have good foot movement, aka Mike Weaver for Holmes, aka Doug Jones for Ali. I think Foreman may be a little too big for Louis but i wouldn't write off Louis. Because look at what Jimmy Young done to Foreman he totally out boxed him and nullified his offense, and Young wasn't that much bigger in weight that Louis was Young was 213, 6'2, when he fought Foreman, and Louis is 6'2 and could weigh 207 and even a little bit more and still be in good fighting shape so don't underestimate Louis.