Jack the Giant Slayer is a kid's story, with grownup action and special effects. There's no blood mind you, just a bit of people eating, and some betrayal, so it's safe for children, but young ones don't need that much fighting. So, you might say it's a movie for tweens. The loving is limited to lip kissing, no tongue, there's a bit of gross humor, the good ones are all good, and the evil ones are all evil.
The special effects and the sets are great, you'll definitively be entertained, and the acting is not so bad, but that's it.
The scenario is simplistic. The characters are shallow, with one track mind. The armors and the defensive "medieval" architecture are not realistic. The dialogs are uninventive. And the end is a disaster. She should have gotten the crown, he has no business having it, and it should end after they kneel. After that, it's diarrhea inducing crap, that doesn't add a shred of substance to the film.
Still, the result is a little bit better than the trailer led to believe.