Let's face it: Star Trek IV and the original Back to the Future were VERY similar. Both involved time travel, both were funny with some tense moments, and both were only a year apart (BTTF-1985, TVH-1986).
The only difference? BTTF had one of the greatest soundtracks of all time, while I found Trek IV's to be not only forgettable, but extremely annoying. At times it sounded as if a circus were doing the music. For Pee Wee Herman, that would be fine; for Star Trek, it was sacrilege of the worst kind, and it more than ruined the film for me.
I found this today on youtube, and now I wish they had gotten Alan Silvestri to do the Trek IV music instead :P