I'm watching the Japanese one on Thursday, but I absolutely loved the American one. As for the comment about them being released simultaneously, it was Ringu and Raisen that were released at the same time, and from all accounts Raisen sucked horribly (not my words, just reviews I've read). Or maybe you're referring to the simultaneous release of The Ring on DVD with Ringu on DVD in the US. Anyway, from what I've read (besides in this thread) there is very little difference between Ringu and The Ring, so I imagine watching Ringu will be like watching Abre Los Ojos after Vanilla Sky, enjoyable but nothing new. Honestly I was hoping Abre Los Ojos didn't have that 10 minutes of explanation at the end, that movie deserved an open ending, all the confusion was wasted when they explained every last detail. I know, I'm watching them in the wrong order, but I didn't know about the originals until the remakes came out.
I want to see Ringu 0 mostly, but there isn't a US DVD of it yet. And I HAVE heard that they're going to make another American one because The Ring did pretty well. Not sure which one they're gonna remake though.