Call me crazy, but I absolutely loved Cry_Wolf! It was the perfect mix of Scream meets April Fool's Day. In fact, I believe it could have, and should have, been the new Scream. Even the new film Smiley followed the same concept (I won't go in to detail to avoid any potential spoilers).
A running theme in the movie was that one of the characters was too smart for their own good, but clearly smarter than the rest of the characters. They were playing chess while everyone else was playing checkers. And ironically, the movie itself ended up being too smart for audiences.
Everyone I talked to about the film after it was released in 2005 either thought it was lame for it's "horrible ending" or it was just "okay". And there where the problem lies, really. Those people didn't "get" the movie. But I don't blame them. It was a thinking-man's movie. Most horror/slasher/thrillers are spoon fed to the audience, so everything is out in front of you. Cry_Wolf asked its watchers to fire up their brains and connect some dots -- and a lot of people didn't.
I personally know a few people who still haven't fully figured the ending out, and it's sad. Cry_Wolf was an extremely smart movie with a great cast of characters who's story is creatively woven in a way that all makes sense.
Now did the film leave room for a sequel? No. But did it have sequel potential? Hell yes. A killer had been created that transcended a specific locale or setting. This killer could be anywhere, awaiting to awoken. It's just a shame audiences didn't get it.