We have had this dicussion on LWOS but here is my view.
It is debatable on whether the RWC is the 3rd largest sporting event, then again it is debatable on whether the Soccer WC is the biggest sporting event too.
It all depends on how you present it.
RWC 2003.
-20 competing nations (from all continents)
-600 players
-TV audience 4+ billion
-Attendance probably 2 million
-profit 70 million pounds
To me the word 'event' means the whole package and its a general saying. If it was more specific like, richest, most attended, largest tv audience then its alot easier to figure out.
The only other events that could be bigger than the RWC are the Winter Olympics and Euro Cup. A list of facts and figures would help in making a more informed decision.