This article shows an image where most popular sport by country can be checked. It's a bit old (from 2006), but I guess not old enough for having changed a lot since then.
Clearly, soccer is the most famous sport worldwide by far, I haven't calculated it precisely, but easily 2/3 of the world population live in countries where soccer is the most famous sport.
What factors have brought soccer to be so famous worldwide? I'd like a brief explanation of why it has expanded so much at cost of other sports, as, although I don't know exactly what were in old times the most famous sports in other countries, it's sure that it's not like a lot of them got to develop soccer or something similar on their own.