In compiling this list of the greatest boxers in history, our editors considered these two factors -- one's boxing achievements and his lasting impact on the sport as well as on mainstream culture. The five finalists were Muhammad Ali, Joe Louis, Sugar Ray Robinson, Rocky Marciano and Sugar Ray Leonard.
1. Muhammad Ali
One of the most powerful imageries in the history of the Olympics was the sight of Muhammad Ali lighting the Olympic cauldron at the 1996 Atlanta Games. Indeed, Ali truly lived up to his nickname "The Greatest". In the ring, he was a masterful fighter. He became the world heavyweight champion at the young age of 22, was later stripped of his title because of his political convictions, and regained his world title on two different occasions. Ali was involved in many of history's greatest boxing bouts including "The Fight of the Century" (against Joe Frazier), "The Rumble in the Jungle" (against George Foreman) and "The Thrilla in Manila" (again against Joe Frazier).
Outside the ring, he was a larger-than-life figure. His confrontational but charismatic personality made him a media darling and a pop icon. His life story and boxing career inspired countless books and movies. Regardless of how you feel about his political stances, one has to acknowledge his significant contributions to boxing. Ali's legacy could be summed up two sentences. People who know boxing know Ali. People who don't know boxing also know Ali.
2. Sugar Ray Robinson
The legendary Michigan native was the most accomplished boxer in history. Sugar Ray Robinson fought in roughly 200 bouts, won 173 times and maintained a knockout rate of 54 percent (all fights). This level of prodigious output is simply unbelievable, since most elite boxers would struggle to even reach 100 bouts. At one stretch of his career, he went undefeated for 130 straight fights! This was in addition to a 40-bout winning streak to start his professional career. Robinson was the world champion in two different divisions -- welterweight and middleweight. In a sport whose spotlight was dominated by heavyweight boxers, Robinson stood out as one of few non-heavyweight fighters who could challenge for the mantle of the greatest. His massive success led to the creation of the boxing term "pound for pound", which is still widely used to this day.
3. Joe Louis
Nicknamed the "Brown Bomber", Joe Louis was the first true black superstar. While he did not have the flashiness of Ali or the flamboyance of Sugar Ray Robinson, he was indisputably the dominant force of his era. Over the course of a career that spanned nearly two decades, Louis amassed 68 victories and suffered only 3 losses -- two of which came after his first retirement from the sport. He became the world heavyweight champion in 1937 and held the title for 12 years -- a feat that remains unmatched to this day. Louis was a very popular champion, drawing praises from both blacks and whites. The reason behind this was his image as a honest and hard working man. Louis' sportsmanship and perceived modesty helped raise the profile of boxing and opened opportunities for other African American boxers.
4. Sugar Ray Leonard
His name, as you might have already suspected, was a nod to the great Sugar Ray Robinson. Leonard's achievement in the ring, however, is just as compelling as that of his idol. The North Carolina native was undoubtedly the most versatile fighter of all time, winning world titles in five different divisions -- welterweight, light middleweight, middleweight, super middleweight, light heavyweight. In addition to his world titles, he was also an Olympic gold medalist winning the light welterweight title at the 1976 Montreal Games. Leonard was also known for being a great role model and ambassador for the game of boxing. Along with Joe Louis, they were boxing's most popular fighters.
5. Rocky Marciano
The man who inspired the popular movie character "Rocky Balboa" was one of very few world heavyweight champions (if any) in history to end his career without a loss or a no-decision. Indeed, Rocky Marciano enjoyed an undefeated professional record. Known as a ferocious puncher, he achieved an astounding knockout rate of 88 percent. Moreover, he started his professional career with 16 straight victories decided by a knockout. However, Marciano's era is generally considered as one of the weakest in history. Most of his opponents were mediocre compared to those of Ali's era for example -- George Foreman, Joe Frazier and Sonny Liston. Nonetheless, Marciano's perfect record is still a significant achievement regardless of the competition. One can't blame him for dominating in a weak era.