For me, I think fantasy, science fiction and horror are fantastic genres to read, but I haven't really had any ideas for stories of my own.
So far, my ideas on what to write about have come directly from my life. I've looked at a situation and said to myself, "There's a story there!". I become interested in the people involved, what motivates them, what I can explore etc...
The only fantasy idea I came up with was given birth in a dream - and it's since faded from memory.
Maybe I should give myself a break. I'm not currently a writer, just thinking about it. Starting with what I know and what is around me is hardly a stupid or unnatural thing.