#3 Ryback
Ryan Allen Reaves managed to get his foot in the door of the business by participating in one of WWE's Tough Enough reality shows. He didn't win due to broken ribs and illness, but he did impress officials enough that he made it to the final ten contestants.
After healing, he was permitted to join WWE's developmental territory OVW. There he initially developed the Ryback gimmick, who was basically just a big muscle guy who ran roughshod over opponents.
When he came to FCW, which was the new developmental territory for WWE, he was given a cowboy gimmick and renamed Skip Sheffield. Skip was actually pretty over with the fans, who loved his good old boy "corn-fed meathead' character.
Then he and fellow NXT rookies -- when it was still a reality show and not a separate brand -- became the Nexus, having a brief but strong reign as an almost NWO type group. But they were buried by Super Cena and split up.
Sheffield would break his leg badly, and spend almost a year in recovery. When he returned, it was as Ryback. The Big Guy failed to catch on, despite a huge push and an IC title reign.
Why he never became a bigger star: Fans had already seen Ryback's shtick from Goldberg; in fact, the fans chanted Goldberg's name during Ryback's matches! Given his limited athletic ability and technical wrestling acumen, Ryback was basically just around for his chiselled physique.