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?
Real Madrid - the obvious choice and is the no 1 club currently
Barcelona - Ofcourse someone can become great only with a great rival on the other side
Man Utd - Now they are shit but they dominated for more than two decades. They are very big in Africa and Asia especially
Liverpool - Even though they have been mediocre in PL for some decades they attracted large set of fan base especially in Australia, US , parts of Africa and Asia. Ofcourse they are comeback kings which made them get a lot of support especially in the past decade
Ac milan - A team that is still big because of nostalgia. So many wonderful players and glory. Sad that serie A fell of like it did.
Bayern - Everyone fears of Bayern and that is their brand of football. They will always be big because even though only a few watch bundesliga religiously they are big in European competitions. They humiliate teams making them attract a big set of audience
From then it becomes hard to rank because they are so many good teams with rich histories and passionate and fan bases. Right now I would say arsenal, Chelsea, inter Milan and city. I don’t think people outside Italy and Netherlands care about Juventus or ajax like they do for PL teams.