This will depend entirely on whom you're asking. Of course, there are technical specifications that can deem a photograph worthy of viewing. Is there noise? Is it in focus? How is the composition? Distracting items in the background? Bokeh? And a million other details that many photographers spend hours perfecting to create that one infallible image. While all of these things are important (indeed, I strive to create flawless images as well), sometimes, the most important aspect of a photograph is its audience. I own pictures that no amount of post processing can fix, and though they'll never be in competition, or next to other works of art to be taken apart and criticized, they'll always have a home in my personal gallery.
There you have it. Not all photos are good, but if beauty is in the eye of the beholder, then all photos can not be bad either. Every picture is important to its intended audience.