There’s fanfic, and then there’s homage.
Fanfic is usually written to satisfy the writer; filled with the fan’s desires of what he’d like to see come to pass. Since the focus is the writer’s satisfaction, it often happens that no one but the writer is satisfied after reading.
Then there’s homage, which is written to honor the original work. Any true fan can appreciate a good homage, and it may even succeed in converting the uninitiated.