Ok, it's late (I had to work 13+ hours today), I'm still awake, and there's nothing on TV....so I thought I'd share.
Something I've noticed and which (I think) helps me better judge my own work.
Make your picture as small as possible while still being able to tell "what it is". Does it grab your focus? Does it "demand" attention? If so, it may be a GREAT picture.
Make it 1/2 size. Now does it grab you? If so, it may be a very good picture.
Make it full size. Now does it grab you and demand attention? It may be a good/ok picture.
(It's better if this is done along with many other pictures as in a "gallery view". Lightroom is great for this purpose.)
There are exceptions to this of course, but look around at other peoples photos/galleries....It's almost always the pictures that stand out when at "thumbnail" size that are the truly very good/great pictures.
Unfortunately, very few (if any) of my pictures will pass the "may be great" test.