Who is the best MMA fighter of all time?
The best MMA fighter of all time is widely regarded to be Georges St. Pierre.
Kazuushi Sakuraba was know as "The Gracie Killer" is considered one of the top 15 in the history of MMA. 
Sakuraba is a great fighter. He began his career with Pro Wrestling.
Sakuraba also competed in all four weight classes and is in the UFC Hall of Famers.
Another great fighter from that era is Fedor Emelianenko, who some consider to be the best MMA fighter of all time as well.
Emelianenko ground-and-pound strategy is considered to be the best in the history of the sport.
Emelianenko still fights to this day, making him one of the longest active MMA fighters of all time
There are a few MMA fighters that are still fighting as senior citizens. The list includes Randy Couture and Tsuyoshi Kohsaka.
Randy Couture retired from MMA many years ago