Although men and women share the same basic physiology, there are still differences that mean men are generally superior in fitness levels and sports performance. A simple look at the world records in athletics for men and women, and the weight lifting records for men and women, highlight the differences.
What is the difference between men and women? Men generally are larger with a greater muscle mass, meaning they are stronger, faster and can jump higher. Other differences, related to sports performance, have women with smaller lung capacity and lower concentration of red blood cells.
Men will not always beat women in competition. Women may have a disadvantage in sports in which physicality (speed, strength, endurance, body size etc.) is a factor, however there are many sports in which skill is the predominant factor in success, and women can be competitive and even beat the men.
One example (and maybe the only example) of when women can outperform men in sport is ultra-distance swimming, in which some of the best performers are female. In this unique case, it appears that the extra buoyancy due to the distribution of body fat gives an advantage to women.