He is an amazing composer! I'm surprised that the music from Spirit:Stallion of the Cimarron wasn't brought up yet. That and the TLK soundtrack are the two most amazing albums out there! I love the end of "King of Pride Rock" when Simba is ascending Pride Rock and the reprise of "Circle of Life" at the end. The "Busa" pieces at the end of "Under the Stars" and "This Land" are amazing as well. I also really love the piece where Simba sees Mufasa's ghost. As for sung pieces, CYFTLT is hands-down, the best.
As for Spirit's soundtrack, although it is only on the expanded version, I love the piece of music while Spirit and Rain are falling in love with each other. It's called "Swimming" on the expanded soundtrack, but "Nothing I've Ever Known" is the same thing except with words on the original. It's an incredibly beautiful piece; I love it!