First, by introducing boys to various sports at an early age, you bring them to the good habit of having a physically active life, which could be the most beneficial thing you might give them. For this, parent will find no difficulty to form a list of sports that can suit all ages.
Second, boys (and men) are by nature more physical and agressiveness is an essential part of a boy's characteristics, and one which is used by others to establish the pecking order. They have to learn to be predators from the beginning to survive (these days girls are coming to this as well). In this sense, sports, especially confrontational sports with body contacts(you can cross out swimming events; with the exception of water polo) mimic real live and prepare the boys for what they will face. Sport is not all about fun. Any parents who had accompanied their kids through one sport for more than one year know that there are hard moments to get through for any sport, and sportmanship is alway about doing the little extra, or in Chinese, "拚一把." There are more moments in life beyond sport that call for the little extra. Doing sports also is a way of training kids to maintain a disciplined life. Look people around you, those you are more aware of, those who are more active and more influential (not merely due to their positions) are more likely sporty.
The traditional Chinese teaching to bring childs (especially boys) are not up to the change of time. We were taught too much "温良恭俭让",and tend to give our kids too much "九分无用加一分有害"的知识(from Tevalishi Lenin). We need to raise boys that can stand out and show their character, not nerdy kids who always stay in the shadow. This is easy to say than to do. For the parents, they need to mend their own way of thinking and doing things, because kids always look up at their parents as their model to grow up.