1) Football: 3.3-3.5 billion fans (Europe, Africa, Asia, Americas, etc.)
2) Cricket: 2-3 billion fans (India, UK, Pakistan, Asia, Australia, etc.)
3) Field hockey: 2-2.2 billion fans (Asia, Europe, Africa, Australia)
4) Tennis: Around 1 billion fans (Europe, Americas, Asia)
5) Volleyball: Around 900 million fans (Asia, Europe, Americas, Australia)
6) Table tennis: Around 900 million fans (Asia, Europe, Africa, Americas)
7) Baseball: Around 500 million fans (US, Japan, Cuba, Dominican Republic)
8) Golf: Around 400 million fans (US, Canada, Europe)
9) Gridiron (American football): 390-410 million fans (US mainly)
10) Basketball: Not more than 400 million fans (US, Canada mainly)
source