With such a blatant, incongruous title, you'd expect this film to be silly, badly made schlock, but the surprising thing is that it's not. Daniel Craig, Harrison Ford, Olivia Wilde and the other actors to a man play the entire thing straight and serious, and you find yourself believing them and buying into the genre mash-up premise which initially you'd be forgiven for thinking sounded cheesy and ridiculous. Not only that but the cast, and in particular Craig and Ford, put in solid, strong performances that give their characters the stamp of depth and three-dimensionality. And there isn't too much time in which to achieve this - the focus is, after all, the action-filled clashes between the eponymous factions of the film's title, but I got the sense that the film wouldn't let itself be rushed and that time was specifically set aside during the first half an hour to establish this authentic Wild West setting and populate it with realistic, believable inhabitants, and then give them their moments to grow and develop later on even as the action with the aliens began to take centre stage. I appreciated that.
The CGI and special effects are done well and are fairly seamless, but the most impressive thing is how they are used. They're used sparingly, and their presence always serves the story rather than the other way around; the film isn't awash with them, which I found unexpected given the comic book basis of the film - again, given the film's seemingly silly title you'd be forgiven for assuming that the film is like every other comic book based movie, with CGI coming at you a mile a minute, but it isn't. Oh, you'll get your money's worth if CGI is what you want - it's done well, it's impressive, and there's plenty of it at the film's exciting climax - but as I said, it serves the story, and wherever it was possible to film a scene without CGI the filmmakers have used the real thing. It just takes the film up just a little bit, lends it an extra stamp of realism and believability.
The plot isn't exactly sophisticated stuff, and that's not a criticism, simply a fact. The goal of the characters is simple: rescue their loved ones and stop the alien threat (and for Jake, find out what happened to him and why). It's a clear cut motivation, and the film executes it extremely well. Every scene has a purpose in advancing this plot, every scene is well acted, shot well, dressed well, and all the elements come together. I wasn't really interested in the subject matter of the story too much at first, but because it was so well put together and well executed, it was an entertaining, satisfying, enjoyable film. All in all I would definitely recommend Cowboys and Aliens.