Same as any fight between a guy from the 50s vs. a guy from the 20s... Rock wins Dempsey is one of the most important innovators in history, huge figure in the history of the sport but he was still fighting at a time when boxing was evolving from the crude grappling of yesteryear to the artistry and skill of the coming decades ... Marciano wasn't fancy but he'd be slick as fuck in 1920 and he'd be incredibly strong