Russell Crowe -- Good Genes Or Good Docs?

Russell Crowe still looks pretty nice, guys.

Here’s a 36-year-old version of the "Gladiator" god at a film premiere back in 2000 (left) and 16 years later ... the 52-year-old leading man in "The Nice Guys" at the Cannes Film Festival earlier this week (right).

"Gladiators ... Mount Up!"

The question is...