I'm not normally one for film series, especially if they go for more than three entries. To me, it becomes tedious, like a trial, to have to sit through story after story after story. Just finish the damn thing already. Now, I know no one forces me to watch these movies, but I'm the type of person who, once I start something, I tend to want to finish it, even if it kills me.
No genre is better at milking a franchise for all it is worth than the horror genre. To date there are eleven Friday the 13th movies, eight Nightmare on Elm Street movies, and eight Halloween moves (counting the third installment, which broke from the Michael Myers canon, and not counting the apparent relaunch of the series by Rob Zombie). There are also more than enough in the Hellraiser cycle. Admittedly, these are series that I don't feel obligated to finish. The first and eighth Jason movies, the first and seventh Freddy movies, and the first two Michael Myers movies were good enough for me. Those series just keep finding ways to not kill off the bad guys, and it becomes very tiresome after a while.
On the flip side, though, the Saw franchise has found a way to break the mold of constantly reviving the same antagonist, by eventually replacing the antagonist with a new character. This leads to the logical conclusion that the Saw series MAY NEVER END. Good lord.
The first installment in the Saw series was a decent and somewhat innovative take on the crime thriller genre. Despite what people say after the fact, the twist ending is something that was quite surprising. I certainly did not expect Jigsaw to be the guy who was "dead" on the bathroom floor. Saw II had an equally interesting twist; it also continued the temporal manipulation concept from the first film. In the first film, some of what we think are flashbacks are actually events that occur concurrently with the bathroom scenes. Similarly, in Saw II, what we think are two plots happening at the same time are actually not.
The third installment is a let down, especially after how good the second one is. I had zero emotional attachment to the characters, particularly the main protagonist. I simply did not care, and only thought of it as a way to get to the fourth film. Saw IV shows marked improvement over the previous entry, but doesn't compare to the first two. Apparently there are two more installments slated, with Saw V being released this year. Part of me hopes that the fifth entry is at least as good as the fourth, and that by the sixth the story is wrapped up.
However, if by the time I die, we're on Saw XLV, I wouldn't be surprised. I would just be bored.