The movies, though following the same story, are completely different. Apparently for the English version they have added bits and chopped and changed bits for their own amusement. Sometimes it made it better, sometimes it made it worse.
The Japanese version deals a lot more with the paranormal and ESP than the English version. And it gets to the point in a lot of places the English one doesn't, for example finding the well in Ringu wasn't hard at all because they knew they were going to look for a well.
The Japanese version relies on very little in the way of special effects, especially on the victims. Which makes Ringu more believable than The Ring for me (I never understood why on earth they shrivelled up when I saw The Ring)>
The English version plays out like a horror movie, The Japanese version feels more like a retelling of an ancient legend in modern terms to me.
In short - The Ring is scary and Ringu is fascinating. I couldn't choose which I like more, they're both far too different. Though I would be interested in seeing the prequel and the sequel to Ringu that I have heard about. Apparently the prequel deals with Sadako (Samara) and how she came to be what she did.