Why remake? I guess it can go either way, really. Either you feel you have something interesting or creative to add to an existing work, or your studio has a hole in your late-summer release schedule that needs plugging and you have millions of dollars to throw at already-rich-as-hell movie stars. The Invasion, a pale imitation of its uneven predecessors (all of which are based on the 1955 serialized novel The Body Snatchers), falls completely into the latter, and decidedly crappier, category of remake ideology.
The first film was entertaining in that whole Twilight Zone way where it's ridiculous, but still kitschy fun. What worked best about it was that one could draw out a clear political message at work in the notion of the emotionless, inhuman replacements unstoppably proliferating. Critics still disagree whether or not the pod people were supposed to represent blind Communist conformity or the American, Red-Scare-perpetrating McCarthyist opposition, but everyone can make a solid argument because at least the pod people had a unified, clear-cut agenda. Unlike the 1956 version, the 2007 version tries to be political by showing characters watch news channels and having people briefly mention current wars, but the political message, if there actually is one, is so muddled that it's completely irrelevant, and what could just as easily have been a time-sensitive examination of the evils of thoughtlessly carrying out an oppressive conservative ideology--both Bushism or Jihadism, take your pick--turns into a rather boring, plodding, by-the-numbers, procedural crap fest.
Most alarming (or laughable, depending on your take) is how well things seem to be going for the planet under alien rule. Once the better part of the human populace has become infected by the alien virus (instead of replaced by pod people, the only reasonable update on this sci-fi classic), the news stations triumph the birth of peace around the globe. Digitally altered footage shows Bush signing peace accords with Chavez. Sectarian violence in the Middle East and Pakistan ceases. A new age of peace and prosperity seems to be in store for humanity, which makes Nicole Kidman's shrill protestations against her infected pursuers all the more ridiculous. Granted, they're trying to kill her child, an irritating little scamp that seems to be immune to the virus, which, of course, makes him a potential "cure" for this "plague." It's like the filmmakers realized they'd developed a too-likable enemy, so they threw in the kid (some test audience probably implored them, "think of the children!") to generate some sympathy for Kidman's character who was obviously losing it. However, I'm going to go on record saying that alien totalitarian mind control and the death of a pathetic urchin are a small price to pay for the best thing that's ever happened to humanity. There's a short debate early on in the film, which may as well have had a subtitle scroll across proclaiming "THE MESSAGE," where Kidman's character and some Russian diplomat discuss what the true nature of humanity is. Is it violence and greed? Is it striving for progress? Kidman argues that humans have come a long way and that she has high hopes for the future, but if this film is any indication of the kind of miserable dreck we as a species are capable of, then she's wrong and we're doomed. I say bring on the alien overlords!