George Lucas’s science fiction adventure is an exhilarating update of Flash Gordon, very much in the same half-jokey, half-earnest mood, but backed by special effects that, for once, really work and are intelligently integrated with the story. By this point, Lucas’s 1977 film has been accused of everything from hazy characterization to crypto-fascism (the finale is, indeed, a restaging of Triumph of the Will), and it has become painfully clear that the film’s apparent naivete is anything but—Lucas doesn’t make a move without the market research to back him up. But it remains the most appealing film in the subgenre it launched, with its finger on something basic and satisfying. PG, 121 min.