When coming up with a new idea for a story I often find that it is not so new at all. Take time travel for example. Time travel has been done to death, yet I feel I have stories that use it in a new way. There are certain aspects that haven't been done before. So, it really becomes a variation on a theme. Still, if I have something original to say using time travel as my vehicle, then it is just a matter of the strength of my writing that will make it exciting for the reader, even though they may have read many time travel tales before.
When it comes to editors and publishers I am not so sure that they can easily overcome their reluctance to read another story in that vein. I have some time travel stories just itching to come out, so we shall see.