Cristiano Ronaldo made history last year when the Portuguese footballer became the first-ever football star to become a billionaire while still playing. Although sports stars are famed for their millions, very few cross the threshold into billionaire status during their careers, with the only two others being golfing legend Tiger Woods and boxing giant Floyd Mayweather. According to figures from Celebrity Net Worth, Cristiano is worth $1.2 billion, which is more than double that of the likes of Sir David Beckham, who is estimated to be worth $550 million.  The sportsman has already splashed the cash, presenting his fiancée, Georgina Rodriguez, with an enormous engagement ring, the diamond of which stretches all the way to the model’s knuckles! The stunning diamond is 30 carats, whereas normal celebrity engagement rings are only four carats, and the public might opt for a one-carat ring. Maxwell Stone, a diamond expert from UK retailer Steven Stone, previously told HELLO! that the ring could be worth an estimated $6.5 million. How did Cristiano make his money? A lot of the …