1. It's funny how many of the Avengers are stiffs. Sure, Iron Man is all wry and meta, and The Hulk, particularly as played by Mark Ruffalo, has genuine pathos and pain, along with a dark sense of humor about his whole predicament. Then there are the rest of them. Captain America is a cheesy dope with a cheerfully dipshitted grin permanently plastered on his face. Hawkeye is so bland I can't even remember what his superpower is, or if he even has one. And then you have Thor, a man-god whose very name has become a shorthand for lunkheaded doltery. (There are thousands of people named Thor in the world who are creative and vibrant and dynamic, but none of us will ever believe any of those things because we are too busy giggling about their name.) Thor isn't even a superhero, really, and his stories never quite take the same form as those of other comic book heroes. He's not a weakling who is given supernatural powers and must figure out how to use them to save humanity. He's just a god who hangs out with other gods in a castle in space, occasionally hopping down to earth to save puny humans. He's a hairy Superman carrying a hammer, for some reason.
2. That is to say, Thor sort has the feel of a dead end as a movie character, which is why it's surprising, as it turns out, just how fun both of his movies have been. The first Thor film, directed by Kenneth Branagh, had just enough silliness and self-awareness to have fun with the ridiculousness of the character, and the sequel, Thor: The Dark World, is even more loopy and funny. The Whedon-ization of the Marvel franchise was, it's now obvious, a genius move, linking genuine fanboy enthusiasm with a healthy awareness of how nerdy all of this is; these movies love and mock in equal measure. And there's nowhere it works better than in Thor: The Dark World. This movie is having a terrific time.
3. The movie itself makes no sense. This time, Thor, who has spent the last couple of years protecting the realm of the nine worlds, or something like that, returns to earth to save Jane Foster, who has been infected with some sort of world-destroying disease that an evil elf lord needs to take over the galaxy. There's no real reason that out of all the trillions of beings in the universe this world-destroying disease would choose Thor's girlfriend as its host except for the fact that Natalie Portman needs to be in the sequel, in various positions of peril. For reasons I still don't quite get, to defeat the evil elf lord, Thor needs to betray his father Odin (Anthony Hopkins) and release his bad-guy-from-Avengers brother Loki (Tom Hiddleston, who has more fun in this movie than anyone) from prison, so they all band together to try to save the world again.
4. The best parts of the Thor movies are when they get away from Asgard and all the Norse weirdness. (Asgard even makes Idris Elba boring.) This one gets considerable comedic mileage out of Thor doing banal human things. Here's Thor dealing with a coat rack; here's Thor fumbling with an iPhone; here's Thor riding on the London Underground; here's Thor trying to have a conversation with Kat Dennings. Much of the humor here comes from Chris Hemsworth's performance; he's light on his feet and appropriately goofy about it, perpetually bemused. It's the secret ingredient that makes these movies work; he takes it just seriously enough, and not a smidge more. The whole cast follows his lead, particularly Hiddleston, whose Loki is such a loopy presence that he's now been the villain in three Marvel movies. He's even a hoot pushing children around.
5. There are some impressive battle sequences in Thor: The Dark World, as you've come to expect for Marvel movies, including a climactic fight that spans literally nine different worlds. (There's a portal involved; it's complicated.) But mostly, Thor: The Dark World is here to make you laugh, against the backdrop of a yet another Battle To Save The Universe. In this, it succeeds, handily. The Marvel movies are on quite the roll, really; you can make the argument that the only Marvel Studios movie of the last few years that wasn't enjoyable was Iron Man 2, and even that had Robert Downey Jr. to carry you along. They've hit on the right tone, that Whedon tone, of deference and celebration mixed with wit and spectacle. A Thor movie might feel like a strange fall fit next to all your Oscar contenders, but I bet you'll enjoy yourself more at this than most of those.