Before even debating the other guys, ranking Usman over Matt Hughes by itself is one of the dumbest things you will see in modern MMA fandom. There's no justification for it.
Matt Hughes beat two guys on that very list and that's just the beginning of why his record is better than Usman's.
9x title fight victories - should be 10 if not for the weight miss technicality - against 6 title fight victories.
Hughes beat 5 UFC champions plus a Shooto champ when that was equally as prestigious (And no, I'm not counting Royce). Usman beat 3. Two of those were long before those guys became championship-quality fighters.
And more subjectively, an elderly, shot Woodley, Masvidal x 2, Colby x 2 and former LW Burns are not amazing title wins.
Hughes has got him for quality and quantity.