It's really hard to scare me...but I liked the amount of horror on Buffy. It worked for the show. The "horror" in Hush was really well done. I didn't find the Gentlemen scary, I found them eerie. That's what I've always loved about Buffy, there was always this eerie sense to it. I feel like the show kind of lost that after season 4. Episodes like Nightmares, Killed By Death, The Wish, Who Are You...just to name a few, felt eerie to me.
But yeah...maybe the show could have had a bit more horror...Angel had a LOT of moments that were pretty damn creepy. Billy was a clear homage to The Shining which I loooved. Also, when The Beast went on his rampage, that was great. And the whole Jasmine arc reminded me of some weird horror movie, it was very "Invasion of the Body Snatchers"esque.