I think George Lucas went overboard with this movie. First and foremost, I think the decision to make the movie as a rollerskate musical was kind of incongruous. Furthermore, while the movie stood on its own, it didn't really make sense as part of the whole story. The first five movies in the story were space opera picaresques, so why make the final chapter a love story about trains? Mind you, the music, dancing and costumes were very convincing, but the sets and special effects didn't really live up to the franchise.
Speaking of the franchise, Lucas made some really odd decisions about it. Opening the movie at the Apollo Victoria Theatre in London on March 27, 1984, was kind of surprising, since it was supposed to debut after Star Wars II. Quite a long wait, or perhaps, not enough of a wait. Turning the music over to Andrew Lloyd Weber, instead of fan-favorite John Williams, definitely seemed jarring. Worst of all, I think, was retitling the movie "Starlight Express."
And it didn't even have Spock in it.
I'm delighted and disappointed at the same time.