What about Basketball
The most popular sport should be measured by the number of players registered with national organisations. There are over 300 Million basketball players registered in China alone and most countries have organised competitions and affiliations. Basketball also qualifies as having a low equipment cost and, unlike soccer, requires both hand and foot co-ordination so it is better training for entry to other sports. Of course it does require a higher level of skill since the goals are so much smaller and it does not encourage the violence on the pitch/court that soccer does.
300 million registered basketball players in China alone? That's one third of their entire population, including enfants and the elderly! I'm not sure I can quite trust that figure. I mean, think of the amount of basketball courts it would have to exist to accomodate 300 million players... The figures don't make sense.
soccer is by far the most popular sport in the world. every country in the world plays soccer, some more or less than others. you said 300,000 registered basketball players in china. sorry but that is impossible. only about 300,000 people in china are capable of playing basketball, and im pretty sure not every single one of them do. and soccer has close to the same popularity as basktball in china. basketball isn't popular at all in brazil and most of south america. it is fairly popular in argentina but soccer is much more popular in argetina than basketball. i would say their are easily 100 soccer fans to 1 basketball fan in south america. europe is without a doubt soccer. the only places where basketball is truly popular in europe are places like lithuania, estonia, which are tiny countries. asia soccer is much more popular. i will give you basketball is more popular in china, but not by much, but soccer is much more popular in the middle east, russia, japan, south korea etc. and then africa there isn't even a contest, every country in africa is obsessed with soccer. your whole argument with registerd players anyway is stupid. do you think people in africa register for soccer...no. but still almost every kid there plays it at some level whether its on a dirt field or with an improvised soccer ball.