That's why I love writing Fan Fiction. It's taking some else's world and adding your own flavour to it. Making it a new world in itself. It's not the best if you're trying to write a novel, but it's a start.
I mostly use writing Fan Fiction as a way to get the creative juices flowing. I'll write a few pages of Fan Fiction, and realize that the characteristics of one character that I'm writing would work great in a new story. A story I can make up all myself. No one else's ideas. After spending a few hours each night typing out a story about classic characters from books I've read a million times over, I start to piece together new ideas for new stories.
One day I'll be writing "Harry Potter Fan Fiction" and the next day I'll have half of an original story made up. A short story, but everybody's got to start somewhere.
I'm not saying writing Fan Fiction will one day make me into a great author, I'm also not saying it won't. I've been writing Fan Fiction sense I could write. I loved writing myself into my favourite TV show when I was a kid, or coming up with alternate endings to movies I would watch. Creativity is in everything.
"[the most rewarding thing about writing is] Being able to share your words and thoughts and [have] other's appreciate them." - J. Kahele
Personally, I don't care if others appreciate my work. As long as I'm proud of it, I don't care what others think. That's probably why I write Fan Fiction more than anything else.
Reference :
http://www.elitebookpromotions.com/interview-with-author-j-kahele/