The ending ruined the entire movie

Rating: 4/10 (17 June 2015)

I was drawn to this movie not from seeing any previews and not by word-of-mouth, but by happening to stumble on many good reviews of it. I saw the generic title, and I'd already seen Paranormal Activity and Insidious (both mediocre horror flicks), but most reviews claimed it was better, innovative, etc. Sadly, this is a similar situation to when an ex tries to get back together with you and claims "it'll be different this time, I promise!"
Now, I will admit, this movie was a lot better than Paranormal Activity. Insidious was alright (also better than Paranormal Activity), but it was also a let-down. Sinister was easily a step up from either.
Interesting premise on the plot, I suppose. I wanna call it original, but I feel like it's been done before. Honestly, up until the ending, it was great. I was on edge the entire time, jumped at every jump scare despite bracing myself for them (and no matter how cheap they were... shame on me), and the tension was HIGH. But... the movie ruined itself. The "twist ending" was awful, and where I was worried about getting sleep tonight halfway through the movie, now I'm no longer worried about that. I'm just disappointed that I ended up wasting almost two hours watching this instead of another movie.
I mean, seriously, I'm going to rant for a second here, but that ending. DURR THE KIDS DID IT! Oh my god. It's one thing to use the death of a child for shock factor (because we all know it works), but on top of that making the children the murderers? Seriously? That's just lame and cheesy. I was more excited and scared to find out how the old-man-murderer was still going and why he was still going. Instead, it's a stupid Pagan deity that's possessing kids to kill their families. Geez.
Even movies like The Strangers was scarier than this. At least it implanted that subconscious fear in the back of your mind: "This could happen to you. This is fairly realistic." Up until the Pagan deity thing and all that, this WAS realistic. Every adult who's lived on their own for any amount of time knows the fear of waking up to find someone in their house that doesn't belong there. It's realistically terrifying. Instead, Sinister delivers some honky Pagan possession that could only happen to you if you're in a family of four that lived in a house where a previous murder (that also has to be in the same vein) occurred AND THEN you moved after that again.
All-in-all, I'll give it a 4/10. The fantastic atmosphere and good job they did up until the end is fantastic and good, but it doesn't matter when the whole thing is just ruined.