First, it's correctly billed as "science fiction horror". Horror can come in two flavors, science fiction and fantasy, and like the dichotomy in general, it hinges on whether the story has scientific plausibility. For example, if a vampire story hinges on a virus, an alien invasion, or a mutation in our species, it would be science fiction horror. If, on the other hand, vampires arise due to some inchoate curse, we're dealing with fantasy horror.
Stranger Things is definitely science fiction. In addition to the campy scientists, we have a teacher giving a great little talk about Hugh Everett's "many worlds" interpretation of quantum physics - that is, an infinitely of possible worlds, much like but subtly different from ours, set off by whatever events. That may not be scientific fact, but it's certainly plausible science theory, and is the bulwark of Stranger Things, and makes it very different from A Nightmare on Elm Street, however much the two may share the same teen horror angst.
Indeed, though much has been made about the homages Stranger Things provides to Wes Craven and the 1980s, it cuts a swath all its own. It needed to be situated in the 1980s, in an age before cell phones with cameras, because the lack of ready contact and photographic evidence is essential to the isolation of our characters and their inability to prove what they know to be true. Thus the 80s accoutrements are not so much homages as they essential conveyors of the story.
I'll be back with more when I've finished the series, but it looks like, once again, Netflix has stepped up with a narrative that soars above what is usually found on the networks and cable, including, in this case, series on the Syfy Channel.
See also Fringe 1.6-1.8: Lando to Fringe
more parallel worlds ... "flat-out fantastic" - Scifi and Scary