To me, it's a subject worth photographing.
Then there's a meaning photographer puts behind the image.
Then composition and lighting.
One could make a photograph of a very boring and meaningless subject with perfect composition. It's still a boring photograph.
One could take a worthwhile subject and produce a perfect image but then if there's nothing to say, then it's just an image.
When both of those elements exist, it has to be composed and lighted properly according to the photographer's vision.
I think someone recently said, we all like to talk about taking great photograph but not spend enough time doing it. Maybe we should.