Pawz writes a well thought out response and it's pretty much right along with my thinking.
A good pet food is the one your pet does well on. You can't judge that by any rating system, it's a trial and error.
It used to be (20-30 years ago) the higher the price, the more consistent the sourcing of ingredients thus the more consistent results in feeding. Now days so many boutique food companies have gotten into the field that that may not be the case.
I generally don't like dog food advisor because I don't agree with their basic premise on what's good and what's bad. That site does a very good job describing what byproducts are and their actual nutritional value, but I strongly disagree with their conclusion that the use of byproducts is an indication that all the other ingredients are more likely to be inferior.
The bottom line is that it goes down to how reputable the company is and how reliable they are in sourcing their ingredients and how religious they are in production protocols and how they formulate and determine "complete" diets.
There is great benefit in the research that has been done and the years of experience by the major food companies (purina, hill's, royal canin, mars, etc.) in evaluating the nutritional needs for many different animal species.