This is by far the weight class with the best depth in the entire UFC. So many arguements could be made for a slew of fighters so just bear with me
1. Mauricio Rua- Maricio Rua is on the verge of domination only comparable to that of Fedor Emelianenko. His record of 18-2 speaks for itself (one loss due to stoppage by ref only because he broke his arm.) Not only has he dominated the other MMA organizations, but not he has set his eyes on the UFC. He has never fought in the octagon, but everyone is waiting for his first match against Forrest Griffen. By the way, he already TKO'd the current champ, Quinton Jackson.
2. Dan Henderson- Henderson will get his shot to earn his third championship belt against Quinton Jackson in UFC 75: Champion vs. Champion. It will go great with his Light Heavyweight and Middleweight belts that he earned from PRIDE. Just knowing that Henderson is a champion in two different divisions proves his versatility. No matter what, he usually finds some aspect of his game that leaves his opponent unable to compete. Like Rua, he has yet to fight in the octagon, however, he has impressive victories over Wanderlei Silva and Renato Sobral.
3. Quinton Jackson- Quinton Jackson is one the the most recognizable fighters in the UFC. That may have something to do the his KO of the most recognizable fighter in all of MMA, Chuck Liddell. Not only did he win that match, he also beat him in a previous matchup. This, however, has been his biggest fault. Liddell is the only great fighter that Jackson has been able to beat. Losses to both Wanderlei Silva and Mauricio Rua prove that he is not yet the top fighter in this division.
4. Wanderlei Silva- Even though Wanderlei Silva is in the midst of a two match loosing streak, he is still one of the better fighters in this division. Those two losses were suffered against Dan Henderson and Mirko Cro-Cop(a heavyweight). Just recently inked by the UFC, Silva will be a main event before long. His resume does include victories over Henderson, Quinton Jackson, and Nakamua, all of which were in PRIDE. Dont be suprised if he makes a run for the belt.
5. Chuck Liddell- The biggest face in MMA showed his age in his last fight, a KO in the first round against Jackson to loose the belt. That one fight, however, does not mean that he is finished. He is still one of the most dominant fighters in the division with quality wins over Tito Ortiz, Randy Couture, Renato Sobral, and Jeremy Horn. His furious pace and brawling style always make him a threat to win. Look for him to come back with a vengience in the same manner as Rich Franklin and Georges St. Pierre did after they lost the belt.
Notables: Michael Bisping, Forrest Griffin, Tito Ortiz, Rashad Evans, Matt Hamill