The intentional humor and boisterous filmmaking save the film which would otherwise be laughable for the wrong reasons.
The performances help, too. Hemsworth makes a fine Thor, a bit remote maybe but appropriately self-possessed given the character at hand and capable of charm. He's also good at the film's intentionally played comedy at Thor's expense. There's even a joke about steroids, in case staring at this super body makes the audience feel too jealous and mortal puny. The situational and physical humor almost always work, though Kat Denning's scientist sidekick is saddled with a few dud "jokes". Tom Hiddleston even manages to make some small sense of the ostensible villain Loki (Thor's brother) which is a feat since the screenplay hasn't even begun to decide how evil, ambitious, angry, hurt, morally confused or mischievous Loki is.
The action scenes are, on the other hand, disappointing. They're under-imagined and occassionally incomprehensible, even while they're easy to enjoy on a moment to moment or aural level (each magic weapon has its own obviously distinct "voice"). The battle on the rainbow bridge may be the worst offender in terms of "what just happened again?" as it reaches the film's climax.
But back to Thor, the man god. He's such a fish-out-of-water as superheroes go, that the question keeps nagging even after it's answered. "Where did he come from?"
The larger answer is the Marvel Universe. Marvel has been a comics powerhouse for many decades but their long term movie plan is modeled not on Asgard but on another magical kingdom, Disney. In the place of princesses we have superheroes, which are happily just as marketable. The key difference, beyond gender, may just be in storytelling. As Marvel grows their movieverse they seem perilously oblivious to the fact that movies, save for rare beasts like Harry Potter, need to be stand alone enchantments.
With each new Marvel movie, and its cumbersome connections to the last and next (Jane Foster is the lead scientist here but her achievements are downplayed in the post-credits tag, which surely has more to do with contractual actor price tags than narrative logic) the movies seem less and less like movies and more and more like introductory chapters to a movie that hasn't even started yet. This may work in the short term but how can it possible pay off in the long term?
After so many introductory chapters, Joss Whedon's currently filming The Avengers (2012), which will unite Hulk, Iron Man, Thor and Captain America, would have to be seven hours long to feel like enough of a middle and an end for all of these beginnings. All of this prep work for a team movie has the unintended effect of making each would be blockbuster feel like disposable bloated chapter in some old pulpy movie serial. (Netflix Instant Watch Alert: Flash Gordon is available and its both hilariously dated cheese and timelessly hunky beefcake: Hello Buster Crabbe!)
If you are planning to see Thor this weekend, see it in 2D. Like most 3D conversions the image is too dark and intermittently off-putting. Hollywood remains determined to make 3D the future of film but so far it only looks sensational in animated films or Avatar (same thing?). Though this technology is meant to add depth, fully immersing you in the imagery, it continues to have the ironic effect of making epic environments feel like tiny dioramas instead; you're NOT inside them, you're a god peering down into them. With that gaudy rainbow bridge as a set fixture, seeing Thor in 3D is a bit like playing with superhero dolls in dimly lit rooms, your floors strewn with glitter. Not that you've ever experienced such a thing.