Related to this previous post: Why is it so hard to admit that something you love might not be perfect? Can't you just enjoy someone's company, or lame, psychologically problematic fantasy novels, or pop music without having to defend it on substantive grounds? Junk food tastes good. Mental junk food tastes good. The fundamental appeal of mainlined sugar and fat (or their fictional equivalents) is undeniable, just as is the fact that too much of the stuff will rot your teeth/brain.
(Full disclosure: I am typing this while listening to Ashlee Simpson, with a cat named after a Harry Potter character in my lap.)
(edited to clarify that Ms. Simpson is not my favorite anything.)