It was called something like "The Greatest Science Fiction Story" or something like that. Some physicist makes a story that resolves into the best possible short story for the person who first reads it, or something. He sends it into an agent, and when the agent opens it he sees a verbatim copy of Nightfall by Asimov
"The greatest science-fiction story ever written" by Eric James Stone
I opened it.
“Read it out loud,” Caleb said.
I looked past my name and began reading. “In my opinion, this is the greatest science-fiction story ever written.” My heart leapt within me, and I continued. “It is undoubtedly the best story you have ever submitted to me. But what on Earth made you think you could get away with submitting a verbatim copy of 'Nightfall' by Isaac Asimov?”