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 7 is pretty easy to me: Real Madrid, Barcelona, Manchester United, Bayern, Milan, Juventus and Liverpool.
I think Chelsea, Arsenal, Inter and Ajax fight for the last three spots.