Why do you say that? And how on Earth is "The Thing" better than "Aliens"?
Because "Aliens" isn't really that good to begin with. The plot was almost 100% ripped off from "Them!", a lot of the alien deaths are stock footage, the characters were all stereotypes (except for Ripley, and that was purely because of Weaver's talent), and the ending with the Alien Queen belongs in a video game.
"The Thing" at least accepted the story it came from, the effects were way better, the paranoia atmosphere truly did scare me, and the ending was great.