Jack the Giant Slayer isn’t a great movie by any stretch, but it’s a fun, escapist adventure that doesn’t take itself too seriously most of the time. Something that struck me as really unusual, though, is that once the story gets going, the plot never depends on major characters holding the idiot ball. There are complications galore, and there’s the dumb sidekick for the villain (think Pinky and Jafar), but generally speaking, the main characters are competent, at least in terms of their respective specialties and common sense. The complications arise not from people doing stupid things when they should know better, but from unforeseen circumstances and the scheming, strength, or skills of their opponents.
People see through poor disguises, get suspicious about the turncoat, take measures to actually protect the kingdom from invasion when they get wind of the danger, and so on.
Compare this to, for example, Prometheus, in which highly trained scientists take their helmets off on an alien planet and try to pet the unidentified creatures they find while they’re lost in an underground warren even though they have a map. Talk about too stupid to live.