Currently, gotta be True Blood. As far out as the story gets it still keeps me hooked and wanting more after each episode. The characters are amazing, and there is some great action horrifically gory moments.
But I remember growing up watching Tales from the Crypt when I was younger before I really even got into horror. I remember being freaked out by it but unable to stop watching lol. A great show!
Gotta mention The Walking Dead as well...don't remember to many shows based on the zombie apocalypse and this one is Damn good.