I first became aware of his work in 1983, when Cycle of the Werewolf was published in hardcover. A very short Stephen King "novel" with astonishing illustrations by Wrightson, my 12-year-old self was obsessed with it from the first time I saw a copy on that bookstore shelf. I saved up my paper route money and bought a copy ($28.95!) and pored over those great and gory images. Even smuggled the book into school to astonish my classmates. I'm virtually positive it was my first King story as well.
A few years later, junior high, I met a guy my age who was a true comic book aficionado. Although a novice myself, I went along with him to comics shops and that's where I learned more about Wrightson (and comics in general; this is precisely when The Dark Knight Returns and Watchmen were being published): his hand in Swamp Thing, Creepshow, "Jenifer" (!!!), and what I think of his masterpiece: his 1983 adaptation of Mary Shelley's Frankenstein.
I can still recall how Wrightson's delicate yet detailed art made me feel dizzy with delight. This was how the Frankenstein story was supposed to look! My god. It was perfect. Unfortunately my copy has been lost to the ages, victim of a wild North Carolina storm that flooded the basement of the house I was living in back in the late '90s (which destroyed a nice chunk of other awesome books as well). I've never replaced it, and I'm not sure why.
The horror world is pouring out condolences and memories of Mr. Wrightson, and it seems by all accounts he was a terrific human in addition to being a master genre artist... and a dashing '70s fellow.
Rest well, Mr. Wrightson