The trickiest thing on Earth.

Classical Music or Jazz can at least be evaluated after (somewhat) objective criteria such as complexity or richness - but those criteria do not apply to popular music.

The sole purpose of popular music is raw pleasure, and complexity is simply not a viable criterion for it - if it was, we should assume that Chuck Berry is crap, because Chuck Berry's songs scarcely use more than 3 chords, most of times the same good old Blues chord sequence : A-D-A-E-D-A-E-and start over.

Yes, that's simple. Simplistic. Primitive. So What ? We all know Chuck Berry is not crap. In fact we all feel that Chuck Berry is incredibly good. But we cannot explain it. It just catches you in the guts, and there's nothing you can do about it.

We should admit the fact that there is simply no way to evaluate popular music beyond the crudest approach, that is: "I like it" / "I don't like it". Period.

There is no such thing as an objective critic.