You need to add The Conjuring to the 2010 section, and possibly Paranormal Activity, they'll end up being the iconic horror movies of that decade. Even though Paranormal Activity has just become a mess.

All of these decades have great movies. I'm gonna go with 80s

Gonna go with the 2000s. I actually enjoyed most of those flicks as they brought horror to a new level. The specific films in that decade which are 'The Human Centipede', 'Martyrs', 'The Ring (US)', 'The Grudge (US)' as well as 'Final Destination', 'Wrong Turn' & 'Blair Witch 2' (which is more different than the first) deserve all a mention in the OP.

Honorable 2000 horror film mentions: 'The Hole (UK)', 'The Hills have Eyes', 'Hostel', 'Cabin Fever', 'Ginger Snaps', 'Mortuary', 'Frailty', 'Tamara', 'Wolf Creek'.

All of them sans the 90's (IT being the exception, same as Dracula)

the 80s absolutely. Not even just the movies themselves, but the sort of ethereal, dream-like quality all 80s movies (especially early 80s movies) possess, just enhances the films SO MUCH. "The Lost Boys" is a great example! Just a joy to watch!

1970's by FAR >>>>>>>

90s. Scream & IKWYDLS 00s and 10s are good too. Older movies aren't really scary tbh

I try not to judge older films by how much they scare me, per se, but more how well they build tension and a sense of anxiety.

70s>>>>>>>>>

90s and 00s but I'm being biased since I grew up in those decades.

The answer is the 80's I mean...

The good sis missed the acclaimed Starry Eyes in the 2010's section