Why was this image taken and what is it trying to communicate? Does it succeed?
Might this image appeal to the type of buyers that I'm trying to reach?
No matter how cool looking a photo is, it's only good if it creates desire, builds trust or communicates in some other way that will increase sales. It's only creative if it sells.
Many photographers have portfolios filled with beautiful models, exciting cars and outstanding architecture. These are not difficult to make look great. They look great from many angles and in a wide variety of lighting conditions. Don't allow yourself to be swayed by the beauty of the subject matter.
Are most of the images in the portfolio obviously from real world assignments or are they images that the photographer probably just did on his or her own, without any time constraints?
I believe that what separates a great commercial photographer from a mediocre one is an ability to consistently deliver believable images that make ordinary people and things look great while at the same time creating images that will increase sales.