Well, blood and guts has nothing to do with scary. The definition of 'scary' is hard to say really. Any movie in this era is not 'scary', like Slip said, the aspect of torture has rose, which is disgusting sometimes...but far from scary. Movies these days are all multi-genre.

The Descent was the best thriller/horror flick I've seen in many many years. If you want a lot of "BOO!" moments, that's a good one...also has some blood. It's just a good movie overall IMO.

But, really, the only horror movie that slightly scared me was The Exorcist, and that was when I saw it in the theater and I was a bit younger. Not gorey or bloody, but 'fucked up' works. Other than that, maybe the first few Freddy, Jason, or Halloween movies. Or possibly The Shining...basically you have to go back into the 80's to find actual scary movies.

Honestly, I'd say the less blood in a movie, possibly the scarier. If a movie is scary, it doesn't need blood or gore at all.

Also, The Haunting, wasn't that rated like PG lol?