I'll say that film music is legit. It's just as legit as the incidental music composers used to write for the theatre. Beethoven, Mendelssohn, Grieg, Tchaikovsky, Sibelius, Shostakovich for example wrote in that genre, so how is film any different? In fact, some composer's best work was in films. I am a big fan of older films (1935 - 1960) and there's no question that a lot of my liking has to do the quality of the music. Where would Bette Davis be without Max Steiner? Or try to imagine those great Hitchcock movies without Bernard Herrmann. There are a lot of film scores that stand just fine on their own, but more often the composer or some other arranger has put the music into a more useful form for listening. Then there are some scores that just are not worth it. For example, I love the old British Hammer horror films...watch them regularly. I also have a disk of music from them, mostly by James Bernard. Hate it -- very difficult to listen to as music, but boy does it work in the film.
Here are a few of my favorite film scores that are just as exciting, beautiful and worth listening to as anything:
1) Franz Waxman, Peyton Place. Try to get the Waxman recording, the Varese Saraband, good as it is, isn't as good as the composer's.
2) Max Steiner, Gone With the Wind. You must find the RCA recording with Charled Gerhardt. This is a really great extended 40 minute suite.
3) Korngold: Kings Row. I love this soundtrack. Again, you have get the Gerhardt, but is it still out there?
4) Korngold, again: Robin Hood. The Naxos is superb.
5) Herrmann: Vertigo. Varese Sarabande is excellent.
Then there are a multitude of compilation disks. I'd seek out the entire RCA film classics series from the 1970's. There were some sensational records made. The Waxman Sunset Boulevard is brilliant.
Don't be ashamed or embarrassed by film music. Frankly some of the best composing in the last century came from the cinema.