Music is art. Lyrics are part of the musical creation, they're not a mere caption set below the painting, they are a part of the whole. You may decide how big a part they are according to your own taste, so that it can affect more or less your perception of a song, and this is something that varies from one person to another.
Those words are called "lyrics", organized in "verses", than it looks like they really have something to do with literature. Being those a literary product, I find it fair to judge them as such.
Being literature a subject of study, and being jobs like the writer or the poet some serious professions, we may think there's a way to look at literature from an objective point of view. Because you study what is objective. You may not care much about these things, but this is exactly what is indeed subjective: your personal interest in these matters.
One may be moved by something that strikes him personally, for reasons that are subjective, and according to this he/she may like specific lyrics that are more emotionally powerful towards him or her.
One may as well be seduced by the sound of words and phrases, or by the way they are put together, with puns and similar tools (I've been trying to justify you, in the end I will just defy you), but this is only a single one of the many, many devices that can be used in a literary product, and does not suffice to make something interesting from a literary point of view.
Also, one may be interested in the informations that the text provides, but you may agree that a newspaper article is not always a literary piece.
I recognize that lyrics must necessarily use some literary aspects over others, for example rhythm and syllabication, that are essential as the lyrics are so tied to the music, as well as a strong and direct imagery to underline certain moments of the song (cant' stop this flame for burning, forever more into the night blistering). But still they have to feature a much wider set of devices and be built upon a solid theme to be of some literary value.
This is my position on these matters. One may be fond of some lyrics without any/few objective reasons and I would never dare to blame him for this, but at the same time I think one cannot say that everything about lyrics is absolutely subjective.
I know that we live in a time when people put together pebbles with chewing gum and call it art just because some critic might have recognized his personal feelings in it (and suddenly things that were made with no expenses at all start to be valued loads of money), as well as when books that are sold in million of copies are called masterpieces just because they sell. The next phrase is a personal thought: actually, I think that art today is in such a wretched state because it's become all about money. But I feel I'm on a Pindaric flight and I understand I'm going more than off topic. I allowed myself to write a post about these things just because I think that the subject is of some value.
To say something in-topic: I agree with who said that ADTOE was a step back in the right direction from a lyrical point of view, the return of Myung being certainly not a case. I am very faithful in JM's work and can't wait to hear his new lyrics.