When I saw the original Japanese Ringu, it scared the living hell outta me. I don't scare easily in movies. It takes something deeply and existentially disturbing to get to me -- it has to be the idea that scares me rather than merely the image or the situation. The American version, The Ring? I found it to be well-made and well-acted, but not particularly scary.
I find, in fact, that by and large foreign horror movies and stories (particularly but not exclusively Asian ones) are far more effective than American ones. It strikes me that foreign films/stories deal in archetypes and iconography from their own cultures and thus feel unfamiliar to me, which helps to build a sense of disturbance and discomfort. Asian countries, of course, have non-European-based cultures, so their symbols feel that much more unfamiliar to me. At the same time, their seems to be a willingness in many other societies to use horror to deal with challenging and truly disturbing ideas that American purveyors tend not to traffic in. Why is that? Well, I'll save my theories on that for another post. And I don't mean to say that there's no good American horror out there. Far from it. Try the work of Thomas Ligotti or Bentley Little (his short story The Washingtonians is a good place to start) for a resonating creepiness that is pent up in the tone and the ideas. At the same time, I do see Asian horror bogging down a bit in ghost stories lately. But if you're looking for something off the beaten track of fear, the kind of thing you've not likely seen before, try the books in the Ring Trilogy by Koji Suzuki (the films were based these) and the movies Oldboy (not a horror movie per se, but definitely horrifying and very fierce) or -- if you dare -- Audition (only watch this if you are prepared for the strongest in scary ideas and horrifying imagery -- I'm not kidding).
There's nothing as scary as a new idea.