When it comes down to it, without a great soundtrack, a movie is nothing. You need just the right song at just the right time to cement that emotional or triumphant moment, and the right score will do that. Can you imagine how meh Inception would have been without the reconstruction of Edith Piaf’s “Non, je ne regret rien” and those whomping trumpets? Trust me, it’d be missing a huge component.
But the music can’t save everything. Some movies are just crap, no matter what. But sometimes, those crap movies get a really amazing set to tunes go accompany it.
In those cases, you just need to close your eyes and listen; no need to pay attention to the flick.