I have a lot more ideas for stories than I have stories.
The ideas come all the time, and they’re all "interesting" in the sense that they present a new twist on an old idea, or exploration of a new one. I keep a running list of them. From an intellectual or gee-whiz perspective, they’re good.
The reason a lot of them don’t turn into stories is that I fail to envision a set of events proceeding from those ideas that really moves me. I can think of characters and a plot, maybe even a theme, but I don’t get driven to write the thing (or not more than a few hundred words) because it doesn’t engage my passions.
Often I have a lot more success with single, evocative images that strike me so strongly that I can’t let them go. Often I don’t know what the "idea" behind the image is, but I feel that I have to write that scene and then see where it leads.
Or, on the other hand, I start with a particular emotional reaction I’m trying to get, and I work backwards — "How would I get a reader to feel that about this?" Highly manipulative, that last one, but sometims it works wonders.
I’ve had half of a first draft of a particular story sitting on my hard drive for nearly a year. I had a clear idea, and a clear set of characters, and I got a few thousand words into it and lost steam. Then, yesterday, I realized the real emotional, painful thing that was behind the story (and *snort* I’d actually begun writing a scene about that very thing, but had deleted it as an irrelevant digression). So now I’m going to start again.