Ten years ago, this sport was practically unheard of. It still is, to the over whelming majority of the sporting public. I wouldn't put much store in the so called "experts" that have put him at the top of the MMA food chain. If he is, then good for him. But we're not exactly talking about a long and storied sport, with a rich tradition, going back decades. It's not that hard to become an expert, in something, if it hasn't been around all that long.
As for being the best known sports man of all time....come on now....Brian O'Driscoll, Paul O'Connell, Roy Keane, Robbie Keane, Padraig Harrington, Rory McIlroy, Eddie Irvine, Alex Higgins, George Best, Paul McGrath...and a good few others, would be far more recognisable to the average sports fan in Brigton, Boston, or Brisbane, than McGregor would be,