As opposed to the films with which it's often compared (such as Hostel or Wolf Creek), Saw has a complex story and a killer with a philosophy. He doesn't kill to "get off" or for pleasure or just for the sake of doing it - he plays his game in an effort to give people a new perspective on life, to show them how valuable and fragile their life is (usually picking his victims based on the wrongs they have committed). In a demented way, his unconventional thinking kind of makes sense, which is what I think makes the series much richer than most people give it credit for. The villain wants to cure, not kill, his victims. He also makes a unique trap for each individual, each one representing whatever atrocity they have committed. So not only is it intense, brutal, cleverly written and completely disgusting and gory (in an over-the-top good way), but it leaves you second-guessing your own morality once it's over, and I can't say that about many movies, let alone a blood-drenched torture flick.