I'm sure this thread has been done at some point. If its been overdone, I apologize. So let's jump right in.
Junior Dos Santos - UFC Heavyweight Champion. He's won 10 straight overall, 9 of those wins in the UFC. He has just one title defense, but he's basically destroyed everyone in his path. Notable victories include Cain Velasquez, Frank Mir, Shane Carwin, Fabricio Werdum, Roy Nelson, Gabriel Gonzaga, and Mirko Cro Cop. Out of his 15 wins, only two have gone the distance. His next title defense will be a rematch against the guy he took the belt from, Cain Velasquez, at UFC 155.
Jon Jones - UFC Light Heavyweight Champion. The 2011 Fighter of the Year has basically annihilated everyone in his path, literally. It hasn't even been a struggle. Notable wins include Shogun, Lyoto Machida, Rampage Jackson, Rashad Evans, Stephan Bonnar, and Ryan Bader. His next title defense will be against Vitor Belfort, one week from tonight. If he is successful it will be his 4th title defense, which is one away from Tito's record for the division.
Anderson Silva - UFC Middleweight Champion. Undefeated in the UFC. 15 wins in the UFC. 10 title defenses, though it should be 11 due to one Mr. Travis Lutter. His next fight is a non title fight at 205 against Stephan Bonnar, and his fight after could possibly also be a non-title catchweight fight against GSP. I think its even possible to say, in my opinion, that Anderson is now at the point where he cares about his legacy more than his UFC Middleweight Championship. What I mean is that I think he's more interested in simply taking big fights than defending his belt. Notable wins include Forrest Griffin, Chael Sonnen (2x), Vitor Belfort, Rich Franklin (2x), Chris Leben, Yushin Okami, and Dan Henderson.
Georges St. Pierre - UFC Welterweight Champion - He's on a 9 fight win streak and has defended his Welterweight Championship 6 times. He's avenged his only two losses with ease and while he hasn't been known for being a finisher, he has completely owned his opponents in the Octagon. His next title defense will be against Carlos Condit at UFC 154. Notable wins include BJ Penn (2x) Matt Hughes (2x) Josh Koscheck, (2x) Matt Serra, Thiago Alves, and Jake Shields.
Benson Henderson - UFC Lightweight Champion - Like Dos Santos, he has only defended his UFC Lightweight Championship one time, a questionable decision against Frankie Edgar. He is a former WEC Lightweight Champion, and he also defended that title one time. He has won all five of his fights in the UFC, and went 5-1 in the WEC. His next title defense is against Nate Diaz at FOX 5. Notable wins include Frankie Edgar (2x), Donald Cerrone (2x), Jamie Varner, Shane Roller, Clay Guida, and Jim Miller.
Jose Aldo - UFC Featherweight Champion - He has defended his UFC Featherweight Championship 3 times and his WEC Championship twice. Undefeated in the WEC at 8-0. He was set to defend his Featherweight Championship at UFC 153 but pulled out due to some moron driving a motorcycle. Notable wins include Urijah Faber, Chad Mendes, Kenny Florian, Cub Swanson, and Mike Brown.
Dominick Cruz - UFC Bantamweight Champion - He has defended his UFC Bantamweight Championship two times, and defended his WEC Championship 2 times. He avenged his only loss to Faber and has won his last 10 fights. His return date is uncertain but will most likely defend his title against Renan Barao, unless Barao defends his interim belt first. Notable wins include Urijah Faber, Scott Jorgensen, Demetrius Johnson, Joseph Benavidez (2x), Ian McCall, and Brian Bowles. Hasn't knocked anyone out since 2008.
Joseph Benavidez / Demetrius Johnson winner - These two will face to determine the first UFC Flyweight Champion next saturday at UFC 152. Both won a fight at Flyweight to get to this spot, Johnson over McCall and Benavidez over Urushitani. Benavidez has won four straight overall and is 3-0 in the UFC. His only two losses are to current UFC Bantamweight Champion Dominick Cruz. Mighty Mouse won is 1-1-1 in his last three fights. Notable wins for Johnson include Miguel Torres, Ian McCall, and Damacio Page. Notable wins for Benavidez include Miguel Torres, Urushitani, and Eddie Wineland.