Maybe they are or maybe not, but what exactly is that article supposed to tell us? I also remember a while ago that some Dortmund official claimed that Dortmund had 10 million fans in Germany alone, which of course is complete bullshit. Often those numbers are based on facebook followers or something like that ...
United and Real are clearly the 2 most popular clubs, then Barcelona and after that there are 8 clubs on about the same level in my opinion (AC Milan, Juventus, PSG, Bayern, Arsenal, City, Liverpool, Chelsea). Ronaldo makes Juventus interesting, but he is probably their only world class player right now and overall the football City plays is much more entertaining.