I think you've gone the wrong direction here - everything popular is overrated, if anything. Because, as we know, not everyone likes the same things so for everything out there you'll have someone who really doesn't like it. And if that thing is really popular, then for that person it'll be overrated. Take Porcupine Tree on this forum. Probably the most popular band (other than DT, athough even that is debatable) on this forum. So when people don't like them (or don't like them as much), they say they are overrated.
Of course, technically, everything is overrated, since if someone dislikes something and another person likes it then that person is "overrating" it, making the term overrated pretty meaningless. I'd say whatever practical meaning it has, it only has at all when there is a huge discrepancy between the popular opinion and what you think. So if there's some band that I really don't like that a few people on this forum like, then I wouldn't say it is really "overrated" because it's not rater that highly (even though, technically, you could say someone liking something that you don't think is any good makes it overrated). But if there's a band I really don't think is any good that everyone on this forum loves, then I might say that it is overrated on this forum.
So yeah, the more popular something is, the more likely it is to be considered overrated. So everything popular is oeverrated is a more relevant description than everything good is overrated.