Good thread , but of course us knowledgeable music people know trying to compare a song with a score is in a way like trying to compare a picture book on a cocktail table with War and peace.They are different creatures. However there are definitely times in films where I enjoyed[not saying better because that can't be judge] a song in a movie more then a score. Will list more shortly, but just off the top of my head SQUIRM-76- ROBERT PRINCE-Beautiful end theme song, moderate score.
Our old friend Bob "Don't Look at Me" Dylan's songs "Knocking on Heaven's Door" and "Billy (I forget which take)" are superior to the strumming drone that calls itself the score to Pat Garrett and Billy the Kid. The songs work brilliantly in the film but the lalalalala stuff leaves me cold and betrays the film. Oh Fielding, where art thou?
One that leaps out immediately: "Labyrinth". Just great David Bowie song after song, meanwhile I can't think of a single cue that stood out for me (except maybe that breif, although unreleased, piece at the end when she tells him he has no power over her) from Trevor Jones' dated [in a no-so-good way] synth score.
Interpreting your question another way, I never cared for the way the wonderful composer Laurence Rosenthal "adapted and conducted" Mitch Leigh's songs to MAN OF LA MANCHA. No wonder it was the only time he was asked to do so. He is much better at composing cool scores like REQUIEM FOR A HEAVYWEIGHT, THE MIRACLE WORKER and BECKET.
TO KIM TONG- In a pure creative sense you are probably nearly right. But there has been I feel very slim or lackluster scores of not much distinction and as I put on my large long lasting thread last year, Many fine songs from films over the decades. So I will give you 90% PERCENT. Because I feel often it is both good scores and good songs and in the long run a good score is more complicated and important to a film then one or two songs. Great thread though.i would be happy to keep it going.
LAST HOUSE ON THE LEFT-72-Is a good example because except for a few very effective mood sounds at the right time, it was a effective score of a bunch of songs that related well to the action on the screen by DAVID HESS.