Spoilers likely abound.
First off, I have to say that the acting for both films was, on the whole, awesome. I don't know why sci fi doesn't get more respect, because you need good solid actors to make it believeable. If Keanu Reeves tells me he's The One, I'm skeptical, but if Anthony Hopkins tells me he's Odin, the Allfather, I go 'yeah, you know what, you are'.
I really liked Thor for being fun and not taking itself too seriously. This is the first Marvel film where they've kept the elements of magic and aliens intact in the story and you need to have a little self-awareness to pull that off. Chris Hemsworth was not only handsome and charming, but managed the more dramatic moments very nicely. Tom Hiddleston was really amazing as Loki, especially since I had recently seen him in Return to Cranford where he was all sweet and blond and curly-haired and smiley, it was a big contrast and a testiment to his acting abilities. I don't know much about Thor as a comic book or Norse mythology really, but I thought Loki was supposed to be a trickster? I would have liked to see him having a bit more fun with the chaos he was causing, but I do get that we're seeing him at his BSOD moment, so I suppose it's understandable.
My one complaint was length of the movie seemed funny. I don't mean the actual running time, because that was fine, but the fact that the movie took place over a few days made it seem a little rushed with character development. I would have liked to see Thor adapting to being powerless over a longer period of time. He learned his lesson really, really fast. I also would have liked a little more of the Earth side of things, and less about Asgard.
But overall, I really enjoyed it and I am looking forward to the Avengers movie.
As much as I loved Thor for being fun, I really liked the more serious tone they took with X-Men. The last couple of movies have been more about how many characters they can cram in and I liked that this movie took some time to concentrate on character development and relationships.
James MacAvoy and Michael Fassbender were incredible. They played so well off each other and, even though I know this is a new continuity, I could see them growing up to be the Xavier and Magneto we know in the future. Except, I don't know what was going on with Fassbender's accent. I could have sworn he was British at the start, but he was very, very Irish by the end. Which doesn't make sense, because movies aren't filmed in order. If he lost the accent halfway through filming, the accent should change from scene to scene, not gradually change over the length of the movie. Conversely, I sort of heart that James couldn't shout 'Erik!' without it being in a Scottish accent.
I really liked the storyline they did with Mystique. Baby!Mystique was adorable! I thought her and Magneto's relationship made sense, and I liked her interaction with Beast. As usual, a few of the minor characters didn't get much to do, but Havok and Banshee were nice to see. I was giggling at all the mythology gags, but I could have done without the Wolverine cameo.
I also really liked that people spoke in foreign languages when it made sense. I can't say how good a job the actors did in German and Russian, but Fassbender's French was very good.
I think half my love of these movies is how people use their powers cleverly and Magneto magnetizing himself to the floor of the jet to keep Charles from falling out made me grin like an idiot.
Between looking through caps of Jane Eyre for icons and watching X-men, I have come to the conclusion that Michael Fassbender acts with his lower jaw.
If you're interested, Nathan Fillion acts with his nostrils. And Tim Roth acts with the angle of his head.