Honestly this is maybe even better than Alien (1979).
It's definitely better than the 1982 version but I'd have normally gave Alien the nod over this one but I rewatched this two nights ago and Alien last night.
The screenplay is superior in The Thing and the pacing is way better. Characterizations are superior.
Alien is great but in truth it's quite a simple movie and the pacing is starting to show it's age. It's true strengths are it's production design, the nostromo sets, the xenomorph creature design and Goldsmith's OST.
Sigourney Weaver is awesome as Ellen Ripley but MEW is equally as good as Kate Llyod.
Might have to crown The Thing (2011) as the best sci-fi horror. Alien (1979), Invasion of the Body Snatchers (1978) and The Fly (1986) are still within contention. Depends on ones mood.