Ah, crap. I can't decide which are my favorites. So I'll just recommend three and hope they're likely to fit your tastes. Equally weighted.
Rudy
Willow
Halo 3
However, if your thing is leitmotif (i.e. "several different melodies that are all used a lot, but they are used in different contexts"), then you should really revisit Star Wars, particularly the Original Trilogy. The different musical themes pop up all over the place. It really is incredible. You might also consider the four Battlestar Galactica soundtracks, which are also rich in leitmotif, particularly the several variations on the so-called "Opera House Theme". Or if you have a really fine ear and can detect very subtle variations, you might try one of Phillip Glass's soundtracks.
Must-hear Soundtracks
Moderator: Marduk