Real Madrid is the clear-cut biggest club in the world by most metrics, and has been for much of the last 60-ish years — despite what other clubs claim.
- 14 Champions League titles, 35 La Liga and 19 Copa del Rey — that's just an unbelievable tradition of success, over a lot of different periods.
- Near-unmatched history of utterly world-class players with 11 Ballon d'Ors between them: Di Stéfano, Kopa, Puskás, Didi, Gento, Netzer, Pirri, Breitner, Butragueño, Redondo, Raúl, Hierro, Carlos, Laudrup, Zidane, Figo, Fenômeno, Cristiano, Modrić, Benzema, and on and on.
- Extremely popular in Hispanophone regions like South and Central America (and increasingly popular in the rest of the world as well, where they would have a historically significant following if games were widely broadcasted in English).
- One for the accountants: highest average rank in the Deloitte money list, ahead of Barcelona and United.
Then you have a second or third tier with obvious candidates like Barcelona, United, Milan, Bayern, Juventus, Liverpool (all of which are active or dormant juggernauts, though the Italian giants have been in decline for the purposes of this discussion for a while now). The standing of Madrid shouldn't matter to fans of other clubs anyway, unless they're following the institutions they do follow for personal bragging rights (which sounds decidedly unromantic), and United in particular is massive enough that folk need to be perfectly secure in themselves — instead of seeing Madrid's
bigness (which doesn't mean much all things considered) as a slight against United. Spare a thought for the lovely peeps who diligently follow actual minnows of club football (in all different parts of the world); there's a lesson to be learned there: big or small, through thick and thin — you support your team, and that's that!