Well, they arent its not like there are millions of league clubs and so 20 to 30 can be "the biggest in the world"
There are a couple of thousand of which 7 or 8 are the biggest in the world.
And Arsenal are not part of them.
Yup.
Off the top of my head.
Bayern Munich
Real Madrid
Barcelona
AC Milan
Juventus
Manchester United
Liverpool
Massive clubs, not just your "well we've won a couple of League titles and got to a CL final" types