Is Superlek the best muay thai fighter in the world? No. There hasn't been a best muay thai fighter in the world since Saenchai
Given the nature of this sport (constantly competing with the best, which means everyone loses and loses often), the only way a fighter can (imo) be best in the world is if they clearly separate themselves from everyone else; where there can be no argument about who is best. An argument for Superlek being the best in the world is an argument that usually can be made for a good dozen others at any given time.
The guy brings up Superlek's wins over certain fighters -- he's also lost plenty of times to this group. They all win, they all lose.