It's pretty obvious that football dominates most of the world with an overwhelming presence in Africa, South America, Asia, and the European Union. On the other hand, cricket fans rule the Indian subcontinent, American football is loved in the United States and ice hockey takes over in Canada. And, Australians are passionate about Australian football.
While it is not an easy task to estimate the exact number of spectators for each sport worldwide, it is very much possible to give a general idea of the most popular sports in the world in terms of spectators with the research data available. Of course, the list is debatable. You can express your opinions about what you consider as the most popular sport as well as the favorite sport in your country.
Looking forward to your comments!