All horror now is not scary, none of it. So off the top of my head are some recommendations!

The Thing
Jaws
Alien
Cannibal Holocaust

Saw IV was crap, except for the ending credits song (I'm serious, the song was by X Japan)

deep in the woods, i watched it in a cinema and crapped my pants ;)

Ooh speaking of scary movies, has anyone seen the White Noise 2 and Pan's Labyrinth? I wanna see one of these and i really can't decide which one ^^

 um...Pan's Labyrinth easily

Thanks!

One Missed Call, the Japanese version

don't bother with part 2 and part 3

Pan's Labyrinth take on the Spanish civil war is quite laughable, the fantasy part of the movie was good but the historical sections were all messed up.

The Ringu trilogy is great. But the scariest Asian movie for me has to be a Korean horror from 2003, mostly cause it was very weird, "A Tale of Two Sisters" (http://www.imdb.com/title/tt0365376/). And some Spanish movies you might not know, I liked "Darkness" (http://www.imdb.com/title/tt0273517/), and two recent ones have been good, look into them if you feel like it: "El Orfanato" (http://www.imdb.com/title/tt0464141/) and "REC" (http://www.imdb.com/title/tt1038988/).

But my favorite is Tesis (http://www.imdb.com/title/tt0117883/). It isn't horror but filled with suspense. Hollywood did a remake named "8mm" (http://www.imdb.com/title/tt0134273/), but I think the original is better.

David Lynch's Eraserhead.

I guarantee you won't leave the room without being disturbed on some level.

Have you ever seen Kubrick's "The Shining".  It's worth a look if for no other reason than it's different from most of the fluff doing the rounds these days.