If you actually think about it HW boxing has been a bit hit and miss for some time, which probably says why the main american interest is on intermediate weights now. Quality heavyweights as follows, the rest are pub debates.
Joe Louis (arguably the best)
Rocky Marciano (argualbly the luckiest because all his contempories were over 40 years old)
Cassius Clay
Mike Tyson (until his hype bubble burst)
Lennox Lewis
Vitali Klitschko (may well have retired now, good luck to him after his featherbedded reign)
Vladimir Klitschko (getting more silly but the results are there)

The rest of the heavyweights for the last 60 years are just pub argument fodder, and long may the arguments continue! As a brit I still reckon our best chance was David Haye (in 50 years of watching our heavyweights), but we've now lost our bragging rights.

Shame really, the middleweights are looking good though!