1. Georges St. Pierre
No matter what happens in St. Pierre’s return from a lengthy sabbatical, he can make a case for being considered the greatest fighter of all-time. Spread across two championship reigns at 170 pounds, “Rush” has compiled a 12-2 record in 14 title bouts under the Ultimate Fighting Championship banner. Both of his losses -- the first to Matt Hughes, the second to Matt Serra -- were later avenged. All told, St. Pierre has spent 2,204 days as the undisputed UFC welterweight champion. He has bested the majority of his contemporaries, including Hughes (twice), B.J. Penn (twice), Josh Koscheck (twice), Jon Fitch, Thiago Alves, Jake Shields, Carlos Condit, Nick Diaz and Johny Hendricks.