I'm going with JFK. Coolness has a shelf life and if you outlive it it starts to spoil. JFK got his melon pureed at the peak of his cool under epic conspiracy circumstances, preserving his cool for all time.

Ali could've held his own and maybe won this matchup had he the good judgement to die in the ring or something but shaking and mumbling his way into the sunset, his coolness is dripping out the leaky radiator of decrepit old age.