It has its fans, no doubt, but I think it's getting blown out of proportion.
I played the first couple games back when they came out and thought they were pretty good, but nothing mindblowing. Just your average jump scare with a more unique setting. I watched the movie and wished I hadn't. Would've liked to see what Chris Columbus could've done with it.
That said the FNAF IP is far, far more of a small niche IP compared to something like Scream, The Conjuring, Romero's Living Dead, The Ring, 13 Ghosts, Sleepaway Camp. Hellraiser, etc. There are a ton of massive, massive properties Universal could pursue that would eclipse FNAF.