Although my journey started in America, the story originated from a novel with the same name by Koji Suzuki. It is a three book series that starts off with a male character. Later, it was adapted into a 5 manga series, a movie, TV series, a remake in the U.S. and Korea, and even a video game. But I'm skipping a few things like the TV series, Korean remake, and the video game. So far, I have read the first novel, four volumes of the manga, have seen both American movies, and 3 out of 4 of the Japanese anthology.
Forgive me if I forget anything as I explain my comparisons. Some of these pieces I haven't seen in a long time, so I'm going from memory mostly.
No matter if the main character is male or female, it all starts the same. Four teenagers watched an unmarked video tape in a cabin and coincidentally they all died a week later. The main character is related to one of the victims and carries the story by investigating the tape. During their investigation, they tell someone close to them about the tape and they end up helping with the investigation (as well as have a deadline of their life tagged onto them with the main character). **spoiler alert** Things heighten when the main character's closest family member(s) view the tape and the search for a resolution on stopping death is quickened. During the investigation, the main character and their partner learn that this is connected to a young girl with extraordinary psychic abilities and her life was very tragic. They retrace their steps to stop the cycle, but unfortunately, one person doesn't make it and the other realizes the solution to the mysterious tape.
From the novel to the American remake, all of these elements are the same in a general sense. In Koji Suzuki's novel, we follow Kazuyuki Asakawa who works as a newspaper reporter in Tokyo. I believe in both movies, the main characters are connected to the newspaper or some sort of news media. Asakawa's partner is a friend by the name of Ryuji Takayama who was a philosophy professor and a self proclaimed rapist. In the Japanese movie, Ryuji is the main character's ex-husband/father of her son. Asakawa is still married and has a daughter and in the movie, the main characters are not married and have a son. Also, the main character in both movies are female.
From the novel to both movies, the curse tape is different. In the novel, it is more detailed and longer. It also has messages in the beginning and end of the tape hinting that there is a solution to stop death after watching the disturbing images. In my opinion, Ringu has a creepier tape than The Ring. There are also different causes of death between the book and movies. One having to deal with shock of a disturbing self reflection on surfaces to heart problems to a new form of the smallpox virus.
The back story of our antagonist Sadako/Samara varies as well. In the novel, she is a hermaphrodite and, in the movie, it is assumed she is fully a woman. Her psychic abilities vary from the novel to the movies. Also, her struggle with her father and relationship with the doctor that was working with him are different between the two. In the movie, her father was responsible for hurting her and tossing her in the well, but in the novel, the doctor raped her and put her in the well. Both forms of media reveal that Sadako/Samara didn't die right away.
As we move onto the sequel of both movies as I haven't gotten around to reading the next novel, the continuation varies. During the hype of Ringu, another director picked up the movie and decided to create a sequel in the same year which ended up not doing as well. Later, the original director went on to make a sequel of his own which had a slightly better reception and totally different direction. In my opinion, Ringu 2 was a slightly better sequel than Rasen. In Ringu 2, we discover that Reiko and her son survived the curse and we follow Ryuji's student Mai as she tries to figure out what happened to Ryuji. Similar events occur and we learn that Reiko's son has picked up Sadako's supernatural powers. This element becomes the focus of the movie. Rasen goes with the virus theory, but is hard to explain how it can be realistically contracted through reading the words of the horrible events or watching the tape. The main character is still Mai and the story remains to make sense as a continuation to the first movie by connecting it with an autopsy of Ryuji. The doctor, Mitsuo, investigating his death and the tapes also has a personal connection to Ryuji. My reasoning for not liking Rasen as much is because it takes a strange twist. Mai and Mitsuo develop a fast relationship which leads to some crazy reincarnation/birth of Sadako and some awkward moments that were way out there. In the end, Ringu 2 followed more of Koji Suzuki's vision from what I've read in my sources. I look forward to finding that out myself.
As for the American sequel, it is nothing like the Japanese sequels. It follows it's own pace, but shares a few similarities to the overall storyline. Rachel (the main character) and Aiden (her son) still survive and remain to battle the mysteries of the ring cycle. They unveil Samara's past a bit more than the first and share a speck of similarity to the original concept. Even though I saw the Japanese sequels after the American, I'm glad they keep the close tie between Aiden and Samara to provoke more of a conflict to the main character, in this case his mother Rachel. The Ring 2 was a decent sequel, but wasn't as strong as the first (most people expect that from sequels anyway). I must confess that I'm not looking forward to The Ring 3D.
I'm assuming the manga series follows closely to the novel as I've gotten further in the manga than the novel series. From my observation, it does match up with a lot of the events that occur in the original movie franchise and continues to intrigue me to delve further in my research. I hope, in the near future, I can add on to my comparison of Sadako's message to the world.