The most important thing to keep in mind about this movie is that it was never meant to stand on it's own. Ring and Ring 2 are halves of the same novel, the screenplays produced by the same author, made by the same director, and released in consecutive years.

In the comments so far, no one has mentioned the novel, or acknowledged just how closely tied these two movies are. Ring 2 isn't a sequel--it's the second half of the same story. they weren't grasping at straws (as some have suggested) to follow a successful movie with a moneymaking sequel, because the movies came out at virtually the same time. It's rather like suggesting that they're making The Lord of the Rings: The Two Towers as a sequel to The Fellowship of the Ring, solely to capitalize on the success of the first one and make more money.

Splitting the novel into two movies makes a lot of sense--in fact I think that almost any movie made from a novel should really be done this way. There's just too much in a novel to make a coherent movie without hacking out too much.

Thus, the only way to watch these two is back-to-back. They can't be viewed as separate. Further, you can't judge the first one by itself because the story isn't complete.

That being said, certain things are clearly changed from the novel. Kurahashi Masami, as far as I've read, wasn't there when Ooishi Tomoko died, so I'm not sure what will happen later in the novel, and how Masami became so central in the second half. I haven't yet been able to see Rasen--the actual sequel to Ring-- and I'm concerned that it seems to consist of only one movie. it's a very long novel and I have no idea how they'll make it work.