There's a scene in Thor: The Dark World which (for me at least) completely encapsulates the film's strengths and it's weaknesses. Early on in the movie Odin, the ruler of Asgard, sends his mischievous step-son Loki to a glittering jail cell to rot for the rest of his life, but about halfway through the movie Thor realizes that he needs his step-brother's help, so he dives into Asgard's bowels to try to convince his frequent adversary to fight with him. The interaction they have in the prison is on some level satisfying but on another deeper level disappointing.
On the one hand, that scene is an improvement over anything in the first Thor movie, which did not grasp the Loki character at all. In that movie Loki was too emo, too sulky; he had schemes, yes, but he didn't play tricks, which is sort of the point of a Trickster God. Here Loki is being dramatic, but he's also fucking with Thor. He's airing serious grievances about his role as the black sheep in the family, but he's doing so while shape-shifting into various guises just to irritate his overly-serious brother. Loki looks at each transformation as a joke, but Thor looks at them as an irritation, which brings some levity to the scene, but also raises doubts about whether or not the two of them can work together long enough to do what they need to do. By stripping Loki of that side of his personality in the first film, it never reached the same level of complexity.
On the other hand, however, that glittering jail cell is very disappointing, because it is generic. You could imagine Hannibal Lecter being kept there, or some rascal from the Star Wars universe. The old Norse myths had Loki being trapped under a mountain with a venomous snake constantly dripping acid into his eyes. That's a very specific image, and it's larger than life; it's fitting for a god. The Dark World might be an improvement over the first Thor movie, but it's far less rich than the original myths that theoretically inspired it. Every time one of the characters in this movie talks about how the Dark Elves want to steal the all powerful aether they might as well be reading aloud a mad-lib; none of those words bring to mind something that seems real or threatening. Because the Thor films have to be integrated into the broader Marvel universe they have to tame the mythical elements that would make his solo stories more epic; it just wouldn't make sense for an actual God to be hanging around with the mere mortals that populate their other films. That trade off might make the other films in which Thor appears better, but it makes his stag outings worse.
There are other examples I could have picked which illustrate the dichotomy between acceptable for a comic book movie / unacceptable for a religious fable. (For example: it's insane that Thor's band of warriors go into battle using swords (as they did in the Norse myths) against enemies with laser bazookas (technology imported from other comic book movies). That sort of visual miscue creates unnecessary mockery: I guess none of them ever heard that old saying about bringing a knife to a laser bazooka fight?) But ultimately I know it's a moot point. There's never going to be a Thor movie which delves into the original mythology; it's all too dark and violent. The closest we might come is something like Valhalla Rising, which doesn't speak very much to the specifics of Norse religion, but embodies some of it's brutal spirit. So if I want any sort of story about Thor the Thunder God I should accept that it's going to be full of flimflam about "dark elves" (whatever the hell those are) and be satisfied if it avoids boring me. That obviously isn't the best case scenario, but I guess it beats having snake venom get dripped into my eyes.