I don't think the horror genre is properly represented in comics like it should be, I mean a lot of comic writers and companies have their roots in horror comics. Movies like Creepshow, Tales from the Crypt and countless others expound on the idea of comic books being either strictly horror stories or a majority of them being horror.
It's not fair for me to act like there aren't any horror comics, because there are some and most of them are about zombies, and sadly most of them are just limited series. Victorian Undead, The Walking Dead, We Will Bury You, The Waking, all zombie comics and only one of them is a continuing series.
I would encourage you to read The Walking Dead, I'm about half way through compendium 1 of the series (the first 48 issues) and I really enjoy it thus far, also the television adaptation airs on Halloween night on AMC.
Though it's small, the horror comic needs to expand from zombies. There is one non-zombie horror comic coming out now that I'm reading that I find enjoyable, and if you're reading this you'd probably like it too: X-files 30 Days of Night. Yup, a crossover where Mulder and Scully investigate the vampires up in Alaska, not a bad comic and certainly has enough vampire action in it to be considered scary.
Go read horror comics, actually buy them, trades, issues whaterver. Buy them and then the companies will make more, because we need them.