I can kind of understand why X-Men director Bryan Singer wanted to tackle a grown-up reboot of Jack and the Beanstalk. There's a lot of potential for amazing visuals with the giant vine that grows up to the sky, and indeed the vine VFX are absolutely spectacular in the film. Plus there are the giants, which could be cool bad guys. But what, exactly, is the story of Jack and his beanstalk? Unfortunately, this movie has absolutely no idea — though it does flail around rather charmingly in the process of failing to develop any coherent ideas or characters.
Jack is a poor peasant whose parents are dead — all he has left of his father are memories of the stories he told about the legends of giants and beanstalks, and an uncle who reluctantly takes care of him. You'd be tempted to say his uncle is an evil stepfather of sorts, except for the fact that he's legitimately annoyed with Jack. They're pressed for money, so he sends Jack to town to sell their last horse and cart. Instead of doing this simple task, Jack wanders into a puppet show, meets the "adventurous" princess, and tries to protect her honor by getting punched by a group of drunken louts. Meanwhile, somebody has stolen his cart. And then a monk gives him a bunch of beans, begs him to return the beans to his monkish order, and steals Jack's horse while the young man stares slack-jawed at his beans.
So that's Jack. He's pretty useless. You know it's not a good sign when you actually sympathize with the guy who is yelling at your hero to shape up or ship out.
Meanwhile, the generic adventurous princess is running away from home. She's being forced to marry some guy who is twice her age — a social climber who doesn't care about anything but getting those beans so he can become king of the giants with some ancient crown that the princess' ancestor made. I'm sure you can see where all this is going. Princess runs into Jack while running away, beans are spilled, and then thankfully we get to watch awesome vine VFX for like five minutes. Jack's house, with the princess inside, is yanked up to the world of the giants — and everybody will have to prove their manhood by going after her and chopping things down and defeating the Neandertal-esque giants.
Unfortunately, nobody's motivations feel anything but rote. Jack wants the princess, the princess wants an adventure, and her fiance wants to rule the land with a giant fist. There are no surprises, other than ones that look like accidents. For example, there are no female giants. We never know why. Maybe they're all gay, or they are hermaphrodites, like leeches. Maybe the females and males look exactly the same. Or maybe, just maybe, nobody thought carefully enough about this movie to bother with female giants. In the same way that nobody thought about the would-be king's motivations. Why does he want to destroy his own kingdom with giants? Isn't he already going to rule the kingdom by marrying the princess? Wouldn't that be a lot easier, and leave him with an intact palace?
What's truly agonizing about Jack the Giant Slayer is that the fantasy worldbuilding is rich and fun — the floating land of the giants is breathtaking, and the beanstalks are like crazy science fictional biotechnology run amok. Honestly the vines are among the most interesting characters in this movie, and are almost worth the price of admission. I also loved the very brief glimpses we got of the giants' understanding of their own history, and why they hate humans — but these are basically swept aside.
Plus, there are great actors like Ewan McGregor as the princess' guard and Stanley Tucci as her nefarious betrothed. They're having a blast and chewing the scenery like there's no tomorrow — even when they have to act against the badly-rendered giants who look like leftovers from The Hobbit.
Overall, Jack the Giant Slayer felt like the rough draft of a movie that could actually have been pretty awesome if somebody had actually thought about the story a little bit. All the ingredients were there. They just didn't get cooked for long enough.