In terms of fanbase, trophies, history and players. I think most of us can agree the top 9 should look a little bit like this(in no particular order):
-Real Madrid -Barcelona -Bayern Munich -Liverpool -Manchester United -AC Milan -Inter Milan -Juventus -Ajax
But who would you place to make it 10? Maybe Arsenal, Benfica, Chelsea, Porto, Man City, PSG? Maybe a South American club? Who do you choose?
top 15 biggest football clubs: EU (7) real, liverpool, barca, united, juventus, milan, bayern
South america (5) river plate, boca juniors, santos, palemras, flamengo
africa (3) sundowns, ahly, zamalek