How about the one-two punch of Dracula and Frankenstein in 1931. Outside of European (and especially German) Expressionism, it seems to me that these two movies made it possible to make movies for mainstream audiences in which the supernatural horror is, within the context of the film, real. The previous reams of “Old Dark House/Scooby-Doo-ending movies would meet the public’s need for scares, but pull their punches at the end with a contrived “rational” explanation. Dracula and Frankenstein made it possible to present movies to mainstream (American?) audiences where the ghosts and monsters are revealed in the end to be … ghosts and monsters.

I’d also give props to Richard Matheson’s original novel I Am Legend (despite the various indignities heaped on it by three generations of filmmakers). Sure, there are antecedents, but I Am Legend made “daylight horror” a commercial possibility. Prior to I Am Legend, almost all horror strived for the Gothic sensibility — age, decay, and degeneracy. Personally, I’d rather watch or read a gothic than a daylight horror any day, but the fact remains, no I Am Legend means no Stephen King or Peter Straub or Clive Barker, no NotLD, no gialli, no slashers, no sexy urban vampires. Almost everything we think of when we think of horror since 1960 comes out of I Am Legend.

I think Val Lewton probably deserves mention, too. He made intelligent horrors that appealed to adults (and especially, women), he provided an outlet for wartime anxiety, and, for good or ill, he invented the jump scare.