There came a moment late into the run-time of Thor: The Dark World, when I thought it had finally clicked why they got a Game of Thrones guy to direct. Drastic things happen in this plot, with the potential to shake up the continuity of the cinematic Marvel universe in a big way. Unfortunately, this being Marvel, they find a way to walk back most of them before the movie's over, more or less restoring the status quo as comic books tend to do. Fans who loved the Marvel movies because they showed us things we've never seen before may start to get disillusioned if Marvel starts going down the path of only giving us what we've seen already. (Kids who have not seen these tropes 100+ times in their life should be fine.)
Fan service, as has been very much noted this year, is becoming a real issue in franchise movies. The writers of Star Trek Into Darkness insist they gave us Khan because people kept asking them about Khan - not because it was creatively the best choice (which it certainly was not). Marvel took a big chance in deconstructing the Mandarin in Iron Man 3...now all indications are that they're walking that back too, for the sake of the most vocal purists. And we all know what happened when Sam Raimi was forced to use Venom "for the fans" (not that he did that great a job with Sandman either).
So I don't know if Marvel planned for Tom Hiddleston to become its breakout heartthrob, but I'd be mightily surprised if his role in The Dark World would be remotely the same if he hadn't. Like a "heel" pro-wrestler who becomes popular in spite of everything, Loki now finds himself, narratively, in a position where he's constantly teasing a "face turn" to join the good side. It'd be unfair of me to spoil where he ends up, but the "will he or won't he" tension is at least mildly more compelling than anything Thor himself has to deal with - a love triangle with Sif is teased and then dropped - though at the same time it threatens to casually brush aside all the bad brother's evil deeds.
It's a good thing Loki's interesting, because the new bad guy isn't. Why you'd bother paying for Christopher Eccleston to stand around in makeup looking unrecognizable and doing next to nothing is beyond me, yet here he is as Malekith, a "dark elf" who looks like the byproduct of Legolas being raped by a Teletubby. His people were around before the universe as we know it existed, so basically he's just pissed that stuff exists. That's his entire motivation. Throw in yet another ancient, powerful object that bestows ultimate power, and yet another cosmic conjoining that only happens every few thousands of years, and you literally have Generic Fantasy Movie Plot 101. As a kid, I used to complain when movies like Masters of the Universe felt the need to involve earth somehow; here, I'm thankful they did so that the generic soliloquizing can occasionally be interrupted by Stellan Skarsgard running around with no pants, or Kat Dennings randomly throwing other people's stuff through dimensional gateways for the fun of it.
The finale, which plays like a game of Portal gone berserk and has characters popping in and out of dimensions, is the movie's cleverest moment, and put a big goofy smile on my face - for a former TV director, Alan Taylor clearly knows how to be cinematic. I'm not sure why Chris Hemsworth sounds like his mouth is filled with straw for the entire second half of the movie, but it's weirdly distracting, as is the fact that he behaves like a perfectly civilized human being now. That's what happens when you fall for the generic love interest, I suppose - Thor would be far more interesting paired with warrior woman Sif, or spunky Darcy, but he loves Jane Foster for her mind. Oh well - Asgardians live a few thousand years (it's emphasized again that they're not gods, presumably so as not to alienate religious audiences), so Sif can just wait around for Jane to drop dead before making her move, if she really wants.