Roman has a star aura that Hangman (And most people, really) only wishes he had lol. Maybe a better comparison would be Rollins/Hangman? I don't consider Rollins that great a promo, honestly, though he's an incredible worker. I think he's mainly over to this degree as a face because of a decade of consistently good performances, and a theme fans love. His actual character blows.
Side note: Ryback was a brief draw until everybody realized he sucked and was an asshole lol. There are lots of guys that can draw for 3-6 months and then fall off. The real stars are the guys who sustain it.