Ryback was recently on an episode of the Buzzards podcast talking about his return to the WWE in 2012 after his brief run as Skip Sheffield in the Nexus. The Big Guy mentioned that there were plans on putting the World Title on him that year but there were reservations that prevented that as Ryback had gotten his ankle injured two years earlier. Apparently, that title change was to happen with CM Punk at Hell in a Cell.
Ryback said that his merchandise was one of the hottest sellers for the company and outshone John Cena's stuff but they would only make so much of it so he was never able to go above and beyond everyone else in terms of sales. He blames the heel turn on his downfall because apparently Vince McMahon told him that he didn't want him selling merchandise as a heel even though people like Seth Rollins (when he was a heel) and Kevin Owens sell tons of it nowadays.
He also had some more vaguely unkind things about Cena as he said that John never did him any favours and that outside of wrestling, he would probably be a much nicer guy but says he's far removed from the character he plays on TV.
Personally, I find Ryback to be such a strange individual that comes across as bitter and I would take anything he says with a grain of salt and certainly not accept it as gospel.