The debate about MMA's finest fighters ever has, is and always will provoke discussion among fans. Much of the debate circles around who is the best "pound for pound" fighter of all time.
These arguments are interesting and thought provoking, but are ultimately speculative, as there is no way of really knowing who would beat who if they could make weight for a fight.
Debate about the all-time best in each weight class is a little more subjective. Most of the fighters considered will have fought each other at least once, so more definitive conclusions can be drawn.
Without further ado, I present my all time best mixed martial artists in the lightweight to heavyweight divisions. This is just my opinion, feel free to comment and get a debate going. Enjoy!
"The Prodigy" may have a career record of 16-7-2, but his record at lightweight stands at an imposing 11-3-1, with three successful defenses of the UFC lightweight strap.
From 2008-2010, he was considered unbeatable in his natural weight class, so much so that fans demanded he step up to 170 and face Georges St-Pierre so that he would be challenged, something Penn had no hesitation in doing.
At lightweight, Penn has notable wins over fellow greats Jens Pulver and Takanori Gomi, as well as former UFC champion Sean Sherk and perennial contender Kenny Florian. He finished all four of those fights, three with his trademark rear naked choke.
When BJ eventually lost the title to Frankie Edgar, it was considered one of the great MMA upsets. Even more surprising to many was that Edgar again bested Penn in their immediate rematch.
Despite these losses, BJ Penn stands out as MMA's greatest lightweight to date
Honourable mentions: Jens Pulver, Takanori Gomi, Sean Sherk
There are only two welterweights who could claim to being the best of all time: Georges St.Pierre (22-2) and Matt Hughes (45-8). Both fighters have had dominant championship runs in the UFC and are both considered to be among the all-time greats of the sport.
Both have also suffered upset title fight losses. Matt Hughes was submitted by BJ Penn at UFC 46 in what would have been his sixth defense, whilst GSP was famously knocked out in the first round against Matt Serra in what is still the biggest upset in UFC history.
What gives GSP the edge over Hughes is his overall record. His only loss aside from the Serra fight was in the first fight between him and Hughes, a loss he went on to avenge not once but twice.
Hughes has had some big moments in his career, including his TKO win over Royce Gracie and then record five title defenses, but he has been beaten by St. Pierre twice, BJ Penn twice and Thiago Alves in the UFC.
St. Pierre seems to be unbeatable at welterweight at the moment, has avenged his only career losses and has a 2-1 record against Hughes. For these reasons, he deserves to be considered the greatest welterweight of all time.
Honourable mentions: Matt Hughes, Royce Gracie
Anderson Silva is without a doubt the greatest middleweight ever to compete in mixed martial arts. He has a 13-0 record in the UFC, a record eight consecutive title defenses and arguably the most lethal and creative striking of any fighter in history.
His highlight reel knockouts of Rich Franklin (x2), Chris Leben, Forrest Griffin and Vitor Belfort are some of the best in history, whilst his underused ground game has been on display in his submission wins over Dan Henderson and Chael Sonnen.
One of most overlooked strengths is his chin. Silva absorbed power strike after power strike from Chael Sonnen and somehow managed to survive long enough to lock in a fifth-round submission.
"The Spider" often faces his opponents with his hands down, as if daring them to hit him. This could be perceived as arrogance but given the strength of his chin, it's a fairly low-risk thing to do.
The dominance and outstanding talent that Anderson Silva has displayed throughout his UFC title run are stuff of legend. No other middleweight has even come close to matching Silva's feats in the cage.
Honourable mentions: Rich Franklin, Dan Henderson
One of the most popular fighters in MMA history, "The Iceman" was also one of the most devastating knockout artists the sport has seen. He is also credited with bringing mixed martial arts into the mainstream, as well as being the face of the UFC.
Had the UFC initiated its bonus awards system a few years earlier, then Liddell would have made significantly more money during his career.
The proud owner of some of the most brutal knockouts seen inside the Octagon, he was also involved in epic contests with Tito Ortiz, Randy Couture and Vitor Belfort.
The Light Heavyweight division of the UFC and Middleweight division of Pride have produced some truly great fighters over the years. Despite an unflattering end to a great career, Chuck Liddell stands out as the best of this exceptionally deep division.
Honourable mentions: Quinton Jackson, Randy Couture, Tito Ortiz, Mauricio Rua, Wanderlei Silva, Dan Henderson, Vitor Belfort
Fedor Emelianenko was far and away the most dominant fighter in the history of the heavyweight division, as well as the entire PRIDE organisation.
He was without a legitimate loss for the first 33 fights of his career and although his days as a force may be coming to an end, the legacy he made in PRIDE will go down in history.
Unfortunately, "The Last Emperor" did not make the transition to the UFC once PRIDE was disbanded.
Despite this, it cannot be denied the Fedor is the greatest heavyweight of all time. He went 14-0 with one no contest in PRIDE, including wins over Minotauro Nogueira, Heath Herring and Mirko Cro Cop.
He also notched first-round finishes against former UFC champions Andrei Arlovski and Tim Sylvia in his post-PRIDE career.
Honourable Mentions: Minotauro Nogueira, Randy Couture, Mirko Cro Cop, Frank Mir, Mark Coleman, Tim Sylvia, Dan Severn