Intrestingly enough, I struggle with the concept of originality quite a lot. I used to write short stories and considered being a creative writing major for a while, but I discovered that everything that I wrote could be looked at and said, oh, that's like the same thing x person wrote. For example, I tried to write a science fiction comedy, and after reading the first page or so I realized I just sound like I'm trying to copy Douglas Adams. Fantasy that I'd try to write would end up sounding like Terry Brooks. Very discouraging.
And then I realized, anything that someone tries to do will most likely have been though of or done by someone else already. It's just the way of the world. It's very much like that one episode of South Park where Butters is trying to be some evil guy and everything he thinks of his side kick tells him that "the Simpsons did it". Everything anyone does, you can take a look at and say "<blank> did it".
I haven't found a solution for this by the way. I've stopped writing stories because of it, I can't really stand looking at my own work and thinking that I'm somehow a fraud. Am I being overly critial and analyzing it too much? Perhaps, but... that's just the feeling that I have.