Supernatural is very popular and people love it. Not sure how it qualifies for underated at all...IMO. I've never seen any past the first season. If there weren't so many options with cable / internet / Netflix I woulda prob got into that show.
Haven't seen Freddy's Nightmare since it was originally on, but even as a kid I remember thinking it was pretty bad.
Wolf and Friday the 13th are prob my fave all time. Those were also on when I was a kid, so it was also just the excitement of seein new "scary" shows.
For me there just isn't anything in recent times that does it for me as far as horror shows.