Good, Better, Best

This morning I got an email from Jonathan Strahan, requesting my story "By Fools Like Me" for Nightshade's Best of the Year anthology. While this is certainly a lovely way to start one's day, it also got me thinking about what constitutes a "best" story. When "Fools" first came out, in the September ASIMOV'S, an on-line reviewer said that it was nicely done but the idea and setting were old. So how important is a "new" idea for a successful story? How important is new technology, a new and different world, vs. strong characters and emotion? Ideally, of course, a story would have both, but most of us can't manage that all of the time, or even most of the time.
"Fools" takes place in what is becoming a standard apocalyptic setting: the world post-global-warming, in which some parts of the Earth are flooded and others have undergone desertification. The story focuses on a very few characters cut off from the rest of the planet, on a very small and personal scale. Does that aid a story, in that there is more room to develop character, or hurt it, in that it becomes "less SF-nal"? I don't know. I do know, however, that among my own 2007 works, I preferred "Fountain of Age." Jonathan Strahan obviously didn't. Who knows why? Best-of-the-year editors don't have to justify their decisions. Nor do they ask the authors, which would easily lead to an apocalypse all by itself.