It's the execution of an idea, not the idea itself, that makes fiction compelling. If it were the originality of the idea, then a bad author handling a good idea would be far more entertaining than a good author with an ordinary idea. Similarly, no movies would ever be remade because the idea has already been done before (and there would be far fewer sequels too). The world would have only one love song, one painted portrait, one photograph of a sunrise and (blessedly) one romance novel if the only thing that mattered about art was unique ideas. But that's obviously not the case, because we are willing to go and see the "plucky ordinary hero defies the odds and brings down the arrogant, evil villains" movie over and over.
Mokalus of Borg
PS - I'm pretty sure there would only be one episode of many TV shows, too.
PPS - Like Bewitched.