The core the film takes place in the '60s, surrounding the Cuban Missile Crisis. This is a mixed bag: the fashion seems pretty spot on, which extends from mini-skirts to the actual character costumes which are generally much closer to their original comic source material than most comic movies these days. The music is pretty nice, but there are some musical cues that aren't period appropriate and it felt wrong to me.
The bulk of the story involves Professor X and Magneto meeting and starting the X-Men with a batch of kids that you mostly don't care about. Jean Grey and Wolverine and Rogue to me are the X-Men. But the X-Men pantheon is huge, and chars like Havoc and Banshee just don't have the same stuff for me. But that's ok because they are minor compared to the Professor, Mystique and Magneto in the scope of the movie.
The story is pretty simple: The psychic and his shapeshifting friend are met by the government official, and build a team to stop a super villain (Kevin Bacon) who is hell-bent on triggering a Nuclear War between the super powers. Mutant Pride! Humans Bad! Let's All Get Along! You know the themes the X-Men play with: they're all here in fairly heavy handed doses.
So here's my thoughts: Emma Frost was weak. I don't know why Mad Men's January Jones missed the mark: she was cold, but boring. It just didn't work for me. When Beast finally gets his ultimate mutation, he looks laughably bad. Watching Magneto make ridiculous faces when he attempts to move whatever giant iron plot device stands in his way gets old. And I don't know what the budget on this one was, but many of the effects were just below what I'd expect from a summer blockbuster.
The good news is that Charles & Magneto's plot is mostly solid and interesting. Watching Prof X hit on chicks as a young man is fun. Magneto's backstory is ground into you, but there are a number of really awesome scenes where he comes off as seriously badass. Mystique is mostly well handled as well. Sadly when all the X-Men pupils are together, things get a little cheesy. But I guess they are supposed to be teenagers. There are also a couple of cute cameos.
My short answer is that I went in with fairly low expectations: The last X-Men was rough — I just wanted a movie better than that. And I really got that and more. I think Thor was a bit more fun. And honestly I'm more excited for Green Lantern right now than either of these.