There are very few movies in history that you can look at and point to and say… There. That one started it. With the “it” being an entire genre (or sub genre) of film. A bona fide lineage of films that follow in its footsteps.
“Halloween” is one such movie.
There are 293 films on IMDb with the keyword “Slasher Flick”. Of those, only 12 were released prior to “Halloween”, of those only six were American movies. Of those six, the highest user rating is “The Gore Gore Girls” at 5.2.
You can be assured that none of those films launched the slasher movie craze that dominated horror through the 80s and most of the 90s.