Personally I've gotta go with Paranormal Activity. So much of the movie is literally just watching people do normal day-to-day stuff, which is supposed to "build suspense," but I just found it incredibly boring. Nothing happens at all for literally half the movie. The plot is the same unimaginative slop of haunted house evil ghost of every generic horror movie of that era. I also hate the whole, "found footage" shakeycam stuff because to me it completely breaks immersion and suspension of disbelief. Does that do it for people who actually believe in ghosts or something?
There's literally not a single interesting thing about the movie, and not even anything fun to critique or make fun of, it's just boring. If you're thinking about watching this movie, instead, go out and watch an empty pool for an hour, then watch the trailer, and you'll have seen everything that the movie has to offer.
I wonder if this like the Seinfeld isn't funny trope. Like, it's awful and boring and unoriginal because it was basically the first horror movie movie to do much of this house cam found footage thing. I say this because I found the movie quite scary when I first saw it (when it first came out), but can see why it would be really boring and derivative today
I saw it in my college theater around when it came out. There were a couple scary parts at the end (enough to cut for the trailer), but for most of the movie I was just super bored.