Any fighter hoping to earn mention among heavyweight greats from yesteryear is met with critical eyes, and must endure likely unfair comparisons to former champions and contenders.
Many of the most famous fighters in boxing cut their teeth in the heavyweight division. And until the wave of popularity currently driving mixed martial arts rolled into town, the Heavyweight Champion of the World (especially when there was only one) was the consensus "baddest man on the planet."
Lennox Lewis, for example, was plagued by such comparisons throughout his respectable career. It didn't help that he had the personality of a wet shoe, and settled into a more cautious and safety-first style before retiring in February 2004. Aside from that though, he was unlucky enough to succeed more exciting and famous American champs Mike Tyson and Evander Holyfield, among a number of other belt-holders generally glossed over by boxing historians.
Whether or not the big men of yore were actually better fighters worthy of the nostalgic invincibility is of course fairly subjective, though the overall toughness of the division in particular eras isn't quite as difficult to determine.
Current unified heavyweight champion Wladimir Klitschko finds himself in the unfortunate position of dominating what is potentially the worst heavyweight division ever.