If Battlefield Earth weren't so technically inane, it would have been OK. The Harrier jets that have been stored without maintenance for 10000 years that fly without any mechanical work was about as laughable as anything gets in the movies.
Well, in addition to it's technical inanity, it's got the whole Xenu/Thetans/Scientology thing attached. If it were sold as pure science fiction, perhaps, maybe, and even then a poor representation of sci-fi. Plus it was like Travolta's own variation of Mel Gibson's Passion of the Christ in that for Travolta this poorly made sci-fi is part of a scientology belief system, or so I've read.