Prokofiev's is a ballet. And a very fine ballet, too, I might add.
I second the recommendation of Berlioz' symphony. It's one of the finer pieces by one of the finer composers.
After the Tchaikovsky fantasy overture, I'm not sure any of the other Romeo and Juliet pieces are terribly noteworthy, though. Berlioz, Tchaikovsky, Prokofiev. Any other R&J's worth listening too? (I've already crossed the Kabalevsky and the Delius off the list, by the way.:smirk