If this was true, then almost every good movie would have to be considered overrated. Most popular movies deserve their fame, but not all.

Exactly what kittyluv57 said. I would like to add that just because something is popular doesn't mean it's overrated. It would be overrated because it gets way too much credit than it deserves. You can't call something popular overrated because you don't like it.

Not if they are worthy of their popularity

No really. Madoka Magica is popular, but not overrated.

Nope. Unfortunately I've come across many who seem to think so.

"Overrated" is in the eye of the beholder. In my eyes (and likely many others), a series that doesn't amount to the praise that it deserves would be overrated, but never for being popular alone. You can say that a series is overrated because you don't like it, because what's overrated is up to you and if you don't like something you most likely won't understand the hype.