The two tennis stars played head-to-head 14 times between 1978 and 1981, competing in the biggest tennis tournaments around the world. The poll of 2,000 adults saw Cristiano Ronaldo versus Lionel Messi, and the England football team versus Germany came second and third. Muhammed Ali versus Joe Frazier, and more recent tennis opposition, Roger Federer versus Rafael Nadal, completed the …