The beginning of the movie was remarkably similar, to a point. I remember saying, "Dear god, the SETUP is even the same!" The kitchen and the room beyond it, in which the TV is located, look JUST the same, right down to clear windows dividing the two. The two girls had pretty much the same conversation. It began differing when the scene (at least to our minds) cut short, while Tomoko (Katie) was still in the kitchen. The Ring drags the scene out much longer, which is actually nice because Tomoko, like Katie, is still found in her room. I guess we're supposed to assume Tomoko got up there, whereas we SAW Katie do it.
The other kids who died were found in a car, where they'd apparently gone to make out. No accident; they just died (with looks of horror on their faces, but none of that half-melting Samara apparently could cause). WAS there a TV in the car? We may never know.
Reiko (Rachel) is pretty much the same, except slightly less confrontational (but then, she IS Japanese). The woman playing her is GORGEOUS. She's extremely tall for a Japanese woman (hell, she was taller than many of the men) and just... beautiful. She's one of the few things I liked better about Ringu. ^_-
Reiko's child, however, is nothing like Aiden. Yoichi is just her kid - and that's it. Other than watching the tape and exisiting, he seems to have no point at all. Aiden, of course, plays a much bigger part in The Ring, as well as being the only character other than Samara herself who displays any real psychic power. The kid who plays Aiden is also a much, MUCH better actor.
Ryuji is Reiko's ex-husband, and so annoying I hardly cared when he finally died. His American counterpart, Noah, was a MUCH more likeable character. Noah (it's never clear whether he and Rachel were married or just had a kid together or what) was a bit fumbling and kind of irresponsible, sure, but he was still a good guy and had a lot of charm. Ryuji is gruff, kind of an asshole, and also randomly psychic. And it was entirely random - like Noah, he doesn't believe Reiko at first, but then suddenly reveals that "he felt something evil, but assumed it was the tape" and that he can read people's minds and stuff. Um. Then why didn't you believe her? Fuckwit. Naturally this means a lot of the nifty stuff Noah went through to finally change his mind, Ryuji didn't.
The video itself is much, much shorter and not nearly as cool. The opening shot of "the ring" is clearly a well. It's not clear at all what it was in The Ring, which made for much better suspense. Also, the images didn't end up telling a story, like they do in The Ring.
The back story behind the woman on the tape (Shizuko/Anna) is very different as well. Shizuko is supposed to be a woman from a volcanic island who is also randomly psychic. She becomes famous when she predicts the volcano's eruptuon, and then undergoes some experimenting via some crooked doctor to prove ESP exists but, naturally, is accused of being a fraud. She commits suicide by throwing herself into the volcano. Eventually they figure out she had an affair with the doctor, as well as a daughter...
...Sadako. In this movie, Sadako is barely a presence. NONE of the back stuff we got with Samara in The Ring is present. In fairness to Ringu, this may be because the background we get on Samara is drawn from Ringu 2 (yes, there was a sequel in Japan...). Still. We see Sadako exactly three times, by my reckoning:
First, in the "vision" Ryuji randomly gets of Shizuko undergoing the ESP experimenting. Some guy starts calling her a fraud, and then rather comically keels over dead. Shizuko turns and says, in the same exasperated tone you'd use on a dog who'd just peed on the carpet, "Sadako! Did you do that!?" Sadako turns and runs toward Reiko (who's seeing the vision too), her hair completely covering her face (um, WHY does she run around like that when she's still ALIVE? I was just waiting for her to trip), and grabs Reiko's arm with her nailless fingers. THAT was the creepiest part of the movie; too bad it showed up right after the cheesy death of the extra and Shizuko's puppy-chiding.
The second time is when they're in the well (which Reiko and Ryuji just climb into on their own and then, for some reason, proceed to try to drain), and Sadako's body comes to see Reiko. A bit prior to this she had a vision in which we see that Sadako's FATHER (not her mother, like in The Ring, whacks her over the head and throws her in the well. Again, she's got her hair over her face. She also looked like she was about eighteen, which was sad. Samara, being ten or however old she was supposed to be, was MUCH creepier for it.
Although I do want to know why Sadako's father bothered tossing her in a well if there's a perfectly serviceable volcano around.
Last, of course, is the famous climbing-out-of-the-TV scene. She does the same walk towards the screen as she did in The Ring, so THAT was freaky. However, once she actually starts the crawling bit out of the TV, the fright factor lessons severely (thus explaining why I could sleep after watching Ringu). For one thing, Sadako isn't waterlogged like Samara, and thus has healthy pink skin. Sure, her nails were torn out, but other than that... she also didn't do the same crawl. Instead she sort of flexed her fingers (and I suppose her scary lack of nails) at Ryuji for awhile. It seemed rather pointless, as it didn't move her anywhere, unlike the fast and scary crawling Samara did. Besides, as Jess said, it's hard to be terrified of nailless fingers when you can HEAR the actress's nails scrabbling on the floor. Sigh.
And that's IT for Sadako. NOTHING else.
When compared to Samara's development (she actually HAD some, unlike Sadako), it makes me wonder a lot more. Without the development, we have no idea why the hell Sadako is doing any of this, other than that she's obsessed both with killing people and with not being able to see. Samara is a child, an evil one maybe, but her actions begin to make sense when you learn more about her. The copying thing makes perfect sense then. In Ringu, there's no real reason copying works, other than that it just sort of does. They don't even point out why it takes seven days before you die. The Ring answered all these questions, and in it, Samara was a character. Sadako is just a plot device.
But I WILL applaud them for not showing Sadako's face at the end. When she kills Ryuji, all you get to see is one eye. THAT was good, and I wish The Ring had done that as well. Although, I thought showing Samara's face when she was still alive was effective (as well as not bringing up questions like, "Why does Sadako run around looking like Cousin It? Why doesn't she walk into things?"), as that little girl was so darn CUTE. Y'know, when she WASN'T being an evil vengeful spirit.
On the whole, The Ring seemed a lot more developed. There were a lot more details in it, and many of the characters were a lot cooler (and didn't have random psychic powers thrown at them to explain various things). The Ring was also a LOT scarier.
One thing I think is particularly amusing about Ringu that couldn't translate into The Ring was what they named Sadako. Sadako is a famous figure in Japan; there are picture books and stories even here detailing her story. Sadako and the Thousand Paper Cranes ring a bell? In this story, Sadako was a young girl who ended up with cancer a few years after the dropping of the atomic bomb. She tried to fold herself 1000 paper cranes in order to be cured (something about the cranes having magical immortal powers or something; I can't remember exactly). She only managed about 600 something before she died. Her classmates made the rest and buried her with them, and there's a monument to her. She's a national figure for peace.
Funny they named another girl who died young and then went around murdering people hideously after her. But alas, there's no figure in American history after which Samara could have been named, so we lose that cultural irony.