Ten Truly Underrated Sci-Fi Movies

What is it about sci-fi movies that always make us give them the benefit of the doubt?

Are we so shallow that it only takes a few laser pistols, flying cars, and matching jumpsuits to get our creative juices flowing? Are we so in love with the ideas behind the futuristic concepts of sci-fi movies that we're willing to overlook massive flaws in storytelling? (That's the crutch that most Trekkies have been leaning on for years.) Or are sci-fi movies just vastly, vastly underrated by critics and audiences who can't get past the androids and nanobots?