The James Bond movie series has existed through 23 films and 50 years, but it's only a film series inasmuch as every movie features James Bond, super spy, as the main character. There are a lot of aspects that show up in most of the movies, but over the years many different actors, directors, and writers have been involved. Plus, thematically, the movies are often quite different. The winking, goofy days of Roger Moore and the modern, serious take on the character led by Daniel Craig barely have anything in common. In fact, the latest Bond movie, Skyfall, even breaks away from the two prior Craig entries in the Bond ouevre.
The first two Craig Bonds were of a piece, but they decided to go in a different direction for Skyfall. Given the lukewarm reaction to Quantum of Solace, perhaps that is for the best. However, the plotting may have changed to a degree, but the very serious, grim take on Bond remains in place. Additionally, this movie is almost a two-hander, as Judi Dench's M is perhaps the spiritual center of the movie. The film explores the decision M has made in her life, and raises questions about where her place in history truly is. Bond is mostly there to protect her from the main villain of the movie, even if Bond also suffers at the hands of M's decision-making in the opening action sequence of Skyfall.
The villain in question is Raoul Silva, played by Javier Bardem, which is a nice get for Bond, as he is an excellent actor, and he excels at playing evil human beings. That being said, while Bardem excels in his screentime, he actually doesn't figure into the movie quite as much as one might expect, or want. He mostly gets a couple of big set pieces and that is that. Given how much power he is shown to have in the movie, it would have been nice to perhaps see a bit more of Bardem. Of course, time that may have gone to Bardem is likely given to Dench, who is excellent in this movie as well.
Early in the movie M receives a message on her computer from Silva telling her to "think on her sins" and this could probably serve as the thesis statement of Skyfall. The nature of what Bond and MI-6 do hasn't really been broached successfully since Goldeneye, the first Pierce Brosnan Bond and one of the better Bond movies, but the Brosnan era quickly devolved to the point where a nuclear physicist named Christmas Jones was prominently involved. The modern Bond is clearly never headed that way. This movie is as grim as the first two Bonds. There's not really any fun in the films anymore, and that is with intention. Sure, there are a couple of action scenes usually, although this movie is more limited in the big, explosive sequences than the first two entries from Craig.
A lot of people had qualms with the latter third or so of this movie, and indeed it feels a bit off, but it is mostly successful if not quite as exciting or interesting as it could be. This is probably the least exciting, dynamic Bond movie in a while, perhaps ever, but that isn't to say it is not a good movie. It's just intent on being smaller and more focused on the emotions of the characters, even the antagonist. It also is interested in setting up future installments of the Bond franchise, which will still involve Craig, who remains plenty serviceable as 007. A new female character is introduced in this movie and it is handled quite well. There's another female character whose existence is just a bummer. Lastly, it should be mentioned that this movie is filmed excellently. It is perhaps the best-looking Bond film, thanks presumably to having a director as accomplished as Sam Mendes involved.
Skyfall is one of the most successful, and critically acclaimed, in the history of the James Bond franchise. While it is a good movie, and a strong entry in the Bond canon, it's not particularly special when it comes to film in general. It's just a solid film that is mostly well-made that just happens to be featuring a major character from film history.