I've been talking shop with a bunch of my friends, trying to get them to take that first leap into the literary waters. One of them said that she only wanted to write something where the bad guys wins. I thought it was a very good idea and proceeded to tell her of an author I heard had done a very interesting storyline where the protagonist and the antagonist were one in the same. I think I messed up, though, because it was similar to what she had been planning. I implored her to write it anyway. There's no way that the stories would be remotely similar. Look at the genre sections in book stores, how many boy-gets-the-girl stories are there? (Actually, I made a vampire-teen joke, but that seemed a little too easy a target.)
There are theories about the number of story types that can be told. Some say seven, some say more. I don't know. What I do know, though, is that no matter the story type, different people will tell it differently.
I really hope that my blunder doesn't keep her from writing her story. I think it's a fabulous idea.