While I do not want at all to downplay Stan Winston's talents, I find your choice for "his" #1 creation a bit troubling. While Stan obviously deserves the credit for making the aliens work so well on that film by bringing them to life, they were not "his" creations. That credit properly goes to artist H. R. Giger who actually designed the original alien (which was only somewhat aggrandized to make the Queen version) and facehuggers. Again, Stan was needed to make them work on film but the fact that they were not his original artwork work make them a bit less than a #1 effort considering all of the completely original designs he generated on this list.