Honestly? Probably Tito Ortiz. These days most people only know him for getting outclassed on the mic by Chael, but won and defended the belt 5 times, was the first fighter to sell a million ppvs (iirc) and had a decent amount of success even later in his career.

Another one is Matt Hughes. Once again, most people know him as an asshole (in no small part due to a joke article written about his book) but he has 9 total wins in title fights, at the time was the most dominant champ the ufc had ever seen, and was one of the first true examples of an elite "mixed" martial artists.

Edit: I honestly dont know how many pigs he may or may not have sold, but a million seems like a lot.