To me, it's only fitting that we mark the UFC's pseudo-centennial (this is really UFC 105, but who's counting?) by honoring the winner of the initial UFC and the greatest fighter in the history of the company, Royce Gracie.
No man dominated the sport quite like Gracie in those early years, and outside of his inability to continue in UFC 3 that earned him his first "loss," Gracie is 11-1-1 in the UFC, his lone loss coming to Matt Hughes.
Of course, that brings up the question of why Hughes did not top Gracie in the rankings the same way he did inside the Octagon? For me, Gracie was too far removed from his prime for this to be a monumental victory for Hughes.
It was a solid win and another notch in the impressive belt of Matt Hughes, but it was the equivalent of beating up Ken Shamrock during the last five years.
What cememted Gracie in the No. 1 spot on this list was when he displayed his dominance. While Hughes, Liddell, Couture and others have succeed with unified rules and structured weight classes, Gracie excelled without those things.
He beat everyone when you could do almost anything to beat your opponent and having an immense weight advantage was just another potential weapon. In all of his initial UFC fights, Gracie was outweighed by at least 10 pound. He was a welterweight taking on everyone from middleweight to heavyweight and making each and every one of them tap.
There is also his pioneering of Brazilian Jiu Jitsu inside the Octagon that comes into play. Gracie introduced BJJ to the world, fighting off his back and cinching in submissions early time he entered the cage. He introduced one of the first wrinkles to the notion of fighting and everyone rushed out to learn how to use and combat Gracie's ground dominance.
In my mind, there is no question that Royce Gracie is the greatest fighter in UFC history.