I wouldn't think it is the complete way to tell but I'd say it's certainly a fair indicator.� I mean, how many massively rich clubs aren't 'big'?Wouldn't a lot of their revenue be gained firstly by large attendances at games + big TV dollars as people around the world watch them and from all the merchandise they sell (in both their homeland and further abroad).Open to being proved wrong but that's just how it seemed to me with no more than a minutes thought behind it.
Why is there 7 English clubs on the list?
Because of the Premiership and its TV rights which are sold worldwide on a revenue sharing principle among the clubs, which in turn gives many of the clubs in the league a good source of revenue they wouldn't otherwise have. That has nothing to do with how 'big' individual clubs are, but more with how the Premier League has managed to position itself in the global sporting market.
Attendances at the games only account for small portions of clubs' revenues. The big money is in the TV rights, and that's where the Premier League is miles ahead of other leagues. And that's why so many people here seem to think that half the Premiership are among the biggest clubs in the world, where in reality few would have even heard of many of them just 15-20 years ago.