Sometimes, the best stories are those where an idea is sparked from reading something and the idea is taken and written in one's own personal style. If you read a lot of short stories in the horror genre, you'll find many repeats of the same basic ideas, but as long as each is told a little differently and characters are developed into real and interesting people, each story has its merits and we enjoy each one. Besides, "originality", like a lot of these terms we all like to throw around so casually, is not a concrete term; it is abstract, difficult to define. Originality is the "creating of unique style and substance" (Wikipedia) and, if we hold to this definition, we are free to see it in a lot of ways.
Anyway, I'm not trying to claim my own work as to being entirely unique and original--I'm only trying to be myself and write what I like to write. I'm also not trying to claim I've figured out the perfect balance of flawed but relate-able characters, perfect story arcs, and language (if anything, I get too caught up in language trying to be a "good writer" and poetic and create unique metaphors and creepy moments, loosing sight of the story); I'm just trying to say that it is difficult to write something that is "different" and get it published.