Forry is revered for many reasons, he is one of the few people who can say that they were there when science fiction fandom started. Forry was the first person ever to wear a science fiction inspired costume to a convention, and along with a few other devoted fans (including Ray Harryhausen, and Ray Bradbury)pretty much laid the groundwork for what science fiction and horror fandom are today.
He was also (via Famous Monsters) a huge influence on many of the people working in the movie industry today.
Famous Monsters was the first magazine to feature behind the scenes interviews with make-up artists and creature designers.
He was also a hell of a nice guy. I met him a few years ago at one of his famous open house days. He had a terrific collection of props and costumes, and would let anybody come and look at them. He even let me try on Lugosi's original Dracula ring.