Since weight divisions stay constant by definition, I say the fighters that go all the way back to the 50's are pretty competetive. However, at the higher weight of heavy, that may not hold given the unlimited size a heavy can fight at today. Howevere, the 90's produced some good heavies whom I think could compete witht he dreadful bunch in there today except maybe for Wlad.

Weight and size are variables in other sports like football and basketball, and I believe the argument for them does not necessarily apply to boxing.

Great question, however, and I realize progressive skills is the real question.