There's a lot of questions about the 'best', but what about the worst? Which film do you think has the worst soundtrack or theme tune? It could either be because you don't like the music, or you don't think it fits the film.
The problem with 'the worst' is that if you don't like something, you try hard to forget it, or don't watch/listen to it again. That makes remembering the ones you don't like difficult.I do remember, however, that I was not keen on the songs from Disney's Tangled. I didn't think the singing was very good, or the lyrics.