"They Live" is one of those movies film professors love to write about. I had a textbook back in film school that basically hailed it as a masterpiece. I've also heard Carpenter called an unsung auteur. There's plenty of good stuff in the movie about control of the media and all that. You can read it as an Orwellian cautionary tale, or a satire of present day society, or whatever. It's robust enough to sustain such readings.
My problem with the film is that (not unlike Starship Troopers) the subtext is better than the text. It's fun to analyze but I don't enjoy the story for its own sake, nor the acting, cinematography, etc. Carpenter's a good filmmaker but this is not one of my favorites in his oeuvre. The surreally long fight scene between Rowdy Roddy Piper and his buddy -- an astounding ballet of ridiculous male bonding and masochism -- is something to watch, though.