Someone disagreeing with you doesn't mean that they're 15, and I never thought Se7en was very good. It was a tedious, overrated exhibition in mediocrity. SAW was to me what Se7en would've been if it were as good as people said it was. Just as SAW haters say they saw their twists coming a mile away, I felt the same way about Se7en, Shawnee and Tobin give stronger performances than anyone in Se7en, and the "silly gore" is part of how no holds barred these movies are. In a time where the market had been flooded with one PG-13 overy Hollywoodized, watered down for the mainstream, ghost flick Ring cash-in after another, the genre needed gritty, uncompromising horror to save it, the SAW franchise is a perfect example.
I don't find them completely implausable, to an extent maybe, but that can be said about practically any movie.