In contrast to Neil Fein (in his comment) I understand the question to be:
How can I be more original?
When it comes to originality, there is a continuum, with plagiarism (and fan fiction) on the one end and originality on the other. But why is not all art original? Or why is not all art derivative? In my opinion, the two tendencies of the originality continuum are the result of two different artist personalities, or two different motivations to create art:
One artist loves and is inspired by the art he perceives, and wants to create more of the same.
Another artist is interested in certain personal or social issues and uses art to deal with these issues (e.g. art as self-therapy or art as propaganda for certain political or social ideas).
The first type of artist, who is inspired to create art by his love for certain individual works, artists, or genres, will always and forever have the problem that his art looks and feels like it was inspired by something else. It cannot ever be original, because its whole purpose is to recreate.
The second type of artist, who is inspired by his experiences or the life around him, will often have the problem that his work falls outside of genre conventions and audience expectations. It may be so unique as to be incomprehensible or irrelevant to any but a few select audience with similar problems or views.
The solution – and ideal work – to me is art that combines both these inspirations and finds a middle ground:
Art that uses a genre or conventions to deal with social or personal issues.
Since, like most authors, you seem to find yourself closer to the end of plagiarism, how can you shift your art more towards originality? The answer is clear, if you agree with my theroy of what causes originality:
Put more of yourself into your work
You do have a life beyond your love for certain artworks, I suppose, so take the blueprint that you have learned in your reading and use it to tell stories from your own life or about the things that you care for in reality.
Sure, even the topics that interest you in real life have been the subject of many books, movies, paintings, choreographies and so on, and no life is so dissimilar of all others as to be totally unique. What will make your writing unique lies in the word "deal with" that I used to describe the original extreme of the originality continuum above. Originality is not that what you write about has never been written about before. But that you
Use your writing to deal with what concerns you
If you are concerned about the safety of your community, or the state of your marriage, or the drought in California, or whatever, use the blueprint of the writings that you love and emulate to find solutions to those problems. And I mean: Don't take the topic and find literary examples and emulate those. But take your reality and try to solve the real problem in writing.
Let's take an example:
Maybe you love fantasy. And maybe, in real life, you have a small child. Now, you notice how in fantasy the heroes are always single young men unbound by familial responsibility. They can just up and go. But you can't. You can't even party with your friends anymore. So you write the story of a man your age with a child your child's age who hears the call to adventure. He must go (or his world will be destroyed by whatever evil you enjoy), but he must take his child along, because the mother was killed / abducted / is busy with doing the laundry. I don't know if you would want to write or read that story – I have and I would –, but it would certainly be original. And I'm sure you can come up with something that interests you.