Director John Carpenter made cinematic history four years before this film with Halloween. Carpenter's The Thing is roughly based on Howard Hawkes's The Thing From Another World, where researchers in a remote, icy region are attacked by an alien organism. This film has the added twist that the organism can replicate whatever it touches. This creates a great conflict between the characters, as no one knows who's a Thing and who isn't.
Oh, and another huge difference is that this film is swimming in fake blood and gore effects. It's very over the top, which to me makes it a lot less scary. But there are plenty of other genuine scares in the film to make it a very effective horror movie.
The Thing came out in 1982, and it should have been more of a hit at the time than it was. Sadly, it came out at the same time the world fell in love with E.T. - a much cuter and more lovable alien than The Thing. The Thing is an immensely fun movie, though, and is the kind of film that would play well at a party with friends and beer. And pizza, to go with all the blood and viscera.