This discussion has come up before, and I did find a list that did it all statistically once, but I cant remember excatly how it went.
I do know that Rugby Union, Tennis, Golf, Basketball, and Cricket were all right up there, BUT Im pretty sure Motor Sport (which it classed as one sport) was regarded as the 2nd biggest..The motorsport catergory took in F1,. Indy Cars, MotoGP and WRC (plus the numerous touring car cjhampionships around the worlkd) so it was no wonder that it was ranked 2nd...
One sport that hasnt been mentioned tho, is Cycling. It was DEFINITELY in the top 5 of the list...Mainly due to support throughout Europe and South America, and the popularity of its major event. The Tour de France is classed as the biggest Annual sporting event (altho some may argue the superbowl or even the Champions League final is bigger)...
But yeah, I know cycling was top 5, and those other sports I mentioned were all in the top 10...Wish I could find the list, it was out of a magazine, so not online, and Im in england, so its a bit far to go home looking for it right now...