Saw isn't classic by our definition of classic. But the first film, in my opinion, is classic due to the compelling storyline and the iconic twist. That film will always be classic to me.
However, when you really think about it, they're the only "horror"/"suspense" films that are either good or decent. I can't remember the last really good horror film that I watched other than a few remakes. At least Saw is trying to be original with their methods and the killers.
I'm hoping six brings everything full circle and we have important loose ends tied up.
http://www.youtube.com/watch?v=YkBwIRQk0vE
Here's a preview of the new Saw game.