Forbes report the 38-year-old Portugal forward earned $218m over the past 12 months.
His contract with Al Nassr is reportedly worth more than $354m per year.
Argentina's World Cup-winning captain Lionel Messi is second on Forbes' list having earned $208m.
Forbes' top 10 also features basketball star LeBron James and boxer Canelo Alvarez, while 20-time tennis Grand Slam champion Roger Federer is the only retired athlete on the list in ninth place.
