Sinister
I’ve intentionally not included Insidious or Paranormal Activity in this list. For me, they are both fine examples of modern horror filmmaking, especially Insidious which I rate very highly. I decided to include Sinister here because, of all the post-Insidious/Paranormal Activity rip-offs to come out over the past four years, I think this one does a few things very well. I really liked the scuzzy 8mm home movie element (you can see why I like Cannibal Holocaust) and seeing this in the cinema was a real thrill. I’ve not revisited it like I have Insidious so I don’t know if this holds up to repeat viewings. I’d like to hope so.