Watched both Ringu and The Ring on successive nights and, whilst there isn't much in it, think I slightly prefer the US version. For me it has the better atmosphere and I prefer the way they solve the mystery themselves rather than the physic flashbacks. I did like how Sadako is largely left to the imagination though, as opposed to seeing Samara's face though, as the idea of something so scary it will kill you is always more effective than a shot of something that is supposed to be so scary it kills you.
Will give Ringu 2 a shot, but from what I've seen none of the others are worth it. I'm not sure how the modern ones could even work as they are very much films of their time, there's something inherently creepy about a found tape, coupled with the glow and hum of a CRT tv, that you can never replicate digitally. Where I grew up you'd sometimes see tape reels tied around railings or lamposts, the rumours were that they were left there by witches and contained curses. Not sure a link to a Youtube video has the same effect.