I might just voice my opinion here. There was obviously a reason the first did so well in theaters. I can't really say why but I'm guessing it was all the build up. They did a very good job on production. They did a great job dressing it up and making it seem like something a ghost would actually do. Not that I really know but I would be scared if any part of what happened in there happened in real life. People screamed at every little part. Even if they weren't scary.
I don't know. BUT, a good movie in my opinion has a beginning, middle and end. This movie lacked that. There was no real climax or legitimate buildup. There was no reason so sit through it and watch it all except for the end which, if you watch on it's own, you wouldn't have missed any key detail. The same goes for all the saw movies.
The only reason people went to see them was because of the gore which, on it's own, would make a much better movie than with the crappy story line that adds nothing to the movies themselves. I can't believe there have been so many of them to be honest with you. I will probably see the last one though because of the 3D (which is unnecessary but will be terriifying) and Chester Bennington has a small part in it

I'm not denying their production ability. Their marketing was exceptional.
Your remarks about SAW were the most incorrect statements I've ever read.