Why is this on the IMDb top 250?

Rating: 5/10 (26 December 2006)

Can someone please explain to me why this film is so great to them? I'm not one to judge others based on their views of what is a great film, but to me, this film was just terrible. On top of that, it makes it on the IMDb top 250 list! (which I have a problem with) If its acting that people rave about, then I thought it was a good film. If its story that people rave about, I ask them why? I also want someone to at least explain to me what differentiates this film from others in the sci-fi, psychological thriller genre. Finally, if someone can please tell me how they consider ever voting higher than a 7 on the film, I would love to know.