When it comes to discussing the greatest of all time in any sport, there is usually contention found when it comes to generation, level of competition and development of the sport at the time. Similar to most sports MMA finds itself contending with those as well as some aspects unique to combat sports. To preface, MMA is a relatively new sport with the first ever UFC event taking place in 1993, but the sport has evolved so much in those 28 years that there are still many generational differences between fighters as new adaptations to the sport continue to this day. Multiple fight promotions have also had many great fighters in the early days of MMA before the UFC became the powerhouse of the sport that hosts the best fighters in the world. There have been many fighters who have left amazing legacies and those who are still making their own, and the debate for the greatness of each of them among themselves is widely disputed. I would say that the criteria for the pound for pound greatest MMA fighter of all time would have to depend on the competition of the weight division(s) that they fight in, their record, their ability, activity time and amount of title defenses, assuming the GOAT would be a long-time reigning champion in their respective weight class.
Common names thrown around for contention of holding the GOAT title include Jon Jones, Khabib Nurmagomedov, George St. Pierre, Anderson Silva and Fedor Emelianenko. All champions in their respective weight classes with win streaks and title defenses spanning years, cleaning out their weight classes and at times moving up or down weight classes for more opponents. Longevity displays an ability to maintain dominance over a career in a sport that is still adapting year to year and dealing with a consistent amount of top contenders year after year. All the champions named earlier had dominant win streaks and showed exceptional ability for years at the top of their weight class. Fighting for longer requires a higher degree of adaptability and dominance as year after year, your opponents have more clues as to how to beat you.
Title defenses are important to consider. A dominant win streak may be impressive, but if only 2 of, let’s say, 8 of those wins are outside of being champion, it indicates that a fighter was going against easier competition than the champ at the time is. Since the title holder is always fighting one of the top 1-3 ranked fighters below them, the competition is always top tier for the weight class. At times certain divisions seem to lack the depth of competition that they may have had before. If a fighter is competing against high ranked opponents, but the division lacks a lot of talent, there is reason to discredit such a dominant reign for those who may be competing against less opponents, but at a much more talent stacked weight class.
As for having a good fighting record, it is fair to say that the record does matter, but numbers on the screen don’t tell you when exactly the losses were accrued, only that they happened. I would say that it is important to consider the time that the losses occurred. Losses early on in a career are common as fighters are still fresh and more prone to mistakes, whereas losses later on are likely due to age. Increasing the amount of fights you have also increases the chances of losing, especially when your opponent now have years of film against you, and the wear and tear of fighting catches up to you. Retiring early is ideal to avoid lasting damage and unnecessary losses, but leaves fans probably wanting to see more of their favorite fighter such as in the case of Khabib Nurmagomedov who recently retired 29-0 after a definitive win over top contender Justin Gaethje in 2020 and a career of dominance in the lightweight division where he cleared out the division’s top fighters. Otherwise, a fighter may end up like former middleweight champion Anderson Silva, who owns the longest win streak with 16 wins, but was unable to pick up his career after a horrific shin break which saw him end his career with five losses and only a single win after the streak.
When it comes to greatness inside the cage, a fighter should be evaluated by all the above criteria as best as possible and however else you may see fit since, at the end of the day, this is a matter of educated opinion or just favoritism if you want. Great fighters are hard to compare unless they are in the same weight class and fight each other in their primes which is impossible to do unless you have a time machine, so it will always be a matter of opinion. But the GOAT is George St. Pierre and I will not hear otherwise from anybody.