It's always nice to find a movie you can watch safely with your kids- that doesn't have sex, or extreme violence or heart-stopping terror. Something with a positive message and admirable characters for your children to emulate. Thor has all that and more.
If you don't have a comic book background, don't worry. Thor may be based on Marvel Comics' interpretation of Norse Mythology, but it's a solid movie that stands on its own. And it's far less crimefighter than it is fantasy adventure.
Thor tells the tale of the Prince of Asgard- an otherworldly domain far from, but connected to, Earth. Thor, the character, is an impetuous hero full of swagger and ready to leap joyously into battle. His brother, Loki, is a more reserved, thinking man. Both vie for the attention of their father, Odin. Through the course of the movie, we see the two very different paths the brothers take, but which both threaten the peaceful kingdom of Asgard.
If you're overly religious, you might be a little worried about Thor and it's "gods". Don't be. The movie deftly avoids the whole "gods" issue even more than the comic book did. The Asgardians, or "Aesir", are a humanoid race gifted with super strength, longevity and advanced, almost magical technology. They have visited Earth before, as well as many other realms, prompting (in the movie) the Nordic legends of Odin and his pantheon. But they aren't gods- they're near-immortals who are fallible and emotional and basically just super-versions of us.
Thor has several redeeming messages. Instead of just fighting evil, the movie's hero undergoes a short journey, to Earth, where he learns humility and self-sacrifice. He is rewarded for this journey and hopefully kids will pick up on the message: being a butthead is wrong. Being good and noble is right.
Thor also shows us the dynamic between father and son- the impetuous Thor disobeys his powerful father and is stripped of his powers and cast down to Earth to live among mortals. A valuable lesson for kids to be sure- listen to your parents. If you don't, you'll eventually see they were right anyway.
But what about violence? Thor is after all a viking-like figure who carries a warhammer and loves bashing his foes with it. There is some comic book violence, but the best thing is none of it is directed by Thor against people. Only monsters. The odds of little Timmy smashing his brother in the head with dad's claw hammer should be minimal.
Sex? None to be had in this film. In fact, Thor is a gentleman who kisses female lead Natalie Portman's hand when he must bid her goodbye- despite the fact they fell in love at first sight. True, Portman's Jane Foster grabs Thor by the face and lip wrassles him, but still, it's very tame and very safe for impressionable children.
Aside from the issue of whether or not your kids should see this, there's the question of will your kids like this. Mine did. Thor is all about fantasy lands and magic and swords and men in armor fighting beasts. There are princes and kings and queens. There's even a badass female warrior, named Sif. It's all very magical and stuff. Little girls will be enchanted, boys will want to watch monsters getting smashed.
How about the 3D? Well, I personally didn't think it needed it. Only a very few scenes really utilized 3D. My kids don't like wearing those dorky 3D glasses, so I think they'll like this much better at the drive in and on DVD/Bluray in a few months.
Finally, you might be wondering how this compares to other superhero movies. Well, it doesn't.
Ironman had a gigalo, alcoholic playboy in the lead. It was all high-tech and heavy metal and humor. My kids enjoyed it, but Tony Stark's sleepover really made me wish for a fast forward button in the theater. Ironman, while in my opinion the best superhero movie ever made, is not kid-friendly.
Ironman 2 wasn't much better... more booze, more babes. And more funny.
The Incredible Hulk? Well... again, they had to throw the sex thing in. Dr. Banner getting a little too excited during some heavy petting. Totally understandable- it was Liv Tyler... but still... not really appropriate for kids.
Batman? Of all the Batman movies, none seem appropriate for small children. Unless you go back to Adam West's 1966 flick.
Superman? Well, Superman Returns was better than most, but still it had to go all supersexy, by introducing Superman's love child by Lois Lane. Again, just not child appropriate.
Thor beats them all. With a hammer of goodness. Four Hammers Up!