The "Ringu" series is a saga, and a morality play, that was amazingly directed by Hideo Natata, and Hiroshi Takahashi. "Rasen" (Spiral) was more poorly done, and is a little disappointing, but is still pretty good. The main problem with the inconsistency of the story line has to do with too many cooks not following the recipe.
You will notice how the books upon which the movies are based do not correspond. They makes for good movies in themselves, but are out of sync. The telling of the story gets more off kilter with each new novel Koji Suzuki writes.
You won't really get where he's going with the story until you read "Loop" (2005), whose movie hasn't been made yet. I hope when they do, Takahashi writes and Nakata directs. As far as I'm concerned, "Rasen" and "Ringu 2" were not up to par with "Ringu" and "Basudai" (Birthday, aka Ringu 0).
For those who want more meaning, "sada" means "pure one" and "ko" means "girl". So who is Sadako? She is the embodiment of duality. Good/evil, man/woman, hate/love reality/ unreality and in fact the merger of demon and woman. You have to read the manga (comic book) series to get the background. That duality is what is frightening, especially to people of regimented views of how the world "should" be. Things that were once thought to be the realm of only men or women have in modern times become blurred. Japan is about 30 years behind us in the change of sex-rolls, etc. This is the underlying theme of the movie
So how do we pick up these ideas? We are of course "infected" by the media, and our thinking evolves, and we are no longer who we were. There is naturally no going back. That is progress, though many fight it. What were once evil ideas, become accepted as every day fact.
So is Sadako a kind of messiah? The evil one? We also have our own dualities. We can find ourselves beside ourselves with anger, or filled with manic euphoria. We can feel so angry we could... Or, our happiness can seem to radiate to all.
I was also really disappointed that in Rasen and Ringu 2 we don't see the wonderful Yukie Nakamura, who just knocks my socks off. Very charming actress. Why we see a substitute in Rasen only makes sense in the context of alternate universes, which may be the point.
Where Suzuki is headed with this remains to be seen. The movies might start wading into "the matrix", which could tie the story lines together. Can he weave these webs into a consistent story? Hopefully he can keep up the good work. Without the right writer, director and cast, you'll get mush. If they do it right, look out!!!.........
As for the American versions...what a disappointment. They just don't get it. The actors were poorly cast. They don't seem to understand how beautiful and quirky people who are very intelligent, can also be really creepy, because they can see and comprehend things faster than the rest of us, but like Cassandra, are sometimes helpless to change things because everyone else is so slow. They live a blessed, but cursed life. Like Sadako, their blessing is also a curse. The tension should lie in pulling us and repelling us. Don't use gore as filler for a poorly written and cast movie. I guess too many studio executives had a hand in the broth.