Well, honestly, movie music will not advance you far as a musician. The music is not made to help people practice- it is made to sound good while the main character steals the bracelet from the tomb (or whatever movie plots do). If you really plan on getting better than the difficulty of movie music, you should turn to classical- it will certainly humble you!
Here are ten beginner pieces, which are usually very popular (in order of how I think of some):
1) Waltz Op. 39 in Ab - Brahms
2) Prelude #1 in C - Bach
3) Pathetique Sonata mvmt. #2 - Beethoven
4) Waltz #19 in A minor - Chopin
5) Kindersczezen (sp)- About Foreign Lands and People - Schumann
6) Prelude #7 - Chopin
7) Prelude #4 - Chopin
8 ) Sonata K. 331 mvmt. 1 - Mozart (longer and harder)
9) Suite Bergamasque mvmt. 3 'Claire de Lune'- Debussy
10) Waltz in E - Brahms
These all may as well be movie themes (actually, a lot of them are) because they are immensely popular and not too tough. For music, go to sheetmusicarchive.net- should all be there.
BTW, some good movie themes are: Cheers, Jurassic Park (main theme), The Matrix 'Clubbed to death', the Truman Show 'Truman Sleeps' (excellent one- similar to Moonlight Sonata mvmt. #1).
The theme from Somewhere in Time actually is Rachmaninoff

- it is his Rhapsody #23 on a Theme of Paganini.