And the comparison between songs and film is a good one. Not sure why anyone would think otherwise.
Because they're completely different forms of entertainment that most people enjoy for entirely different reasons, and books and movies are two different forms of story telling with their own advantages and disadvantages. I don't listen to music for its story (unless it's a concept album, in which case I'll actually care about the lyrics as far as how well they tell the story).
Yes, but there are multiple ways of enjoying both film and music. There are multiple elements going on at the same time that can be analyzed individually or as a whole.
With film, there is the cinematography, directing, dialogue, writing, acting, special effects, etc.
With music, there is the songwriting, composition, technical difficulty of the music, technical ability of the musicians, the quality of the performance, the lyrics, the delivery of the lyrics by the vocalist(s), etc.
There are comparisons to be made there, and valid ones, regardless of the difference of the media.