What makes a great photograph? An image that moves you is a great one. No matter what the image is of or who is in it; if it moves you in some way then it has done what a photo should. There are lots of photos that simply represent our day to day; and those are important to have. But then there are the images that make you stop and feel. As a photographer, that is what we try to do.
All photographers are different. Some love to shoot landscape, others architecture, under water, weddings or family. No matter what the subject, it needs to move the viewer. You as the viewer know what you like; so even if a photographer has caught a great image it may not be to your taste. Photographers are as different as us; each has a personal taste for what they like to shoot. As far as dog photography goes; emotion is a biggy for me.
I love to shoot dogs. There is so much emotion in dog photography if you focus on the moment. I love the special moments the most; an emotion shared between two. Perhaps another dog or a person; a clear and emotional interaction is a moment to capture. It can be a regular boring time of day but the emotion shared between two, awesome.
For me, candids are where it's at. No posing, no set up, no props; just capturing a life moment unfolding naturally. Of course catching a moment can be tough; practice is where knowing when comes in. Patience is needed for shooting canines. Having a passion for what you're shooting helps with patience. I could literally sit and watch dog from sun up to sun down.
Some photographers have a good eye, others not so much. Like anything, there are good and bad photographers. There are those who can see the moments; while others miss the moments and simple take pictures. Many photographers have lots of big expensive equipment but miss the mark as far as getting great photos.
Capturing great photos is not only done by professional photographers. If you open up to see the moments, then you can save them. If a life moment moves you, shoot it.