Food criticism is a field in the sense that there are a lot of people practicing it, pro and am, but it differs from other areas of criticism in that it is lacking in a long tradition of academic scholarship. The notion of a food writing collegiate course has only emerged in the past few years, and nobody's offering a degree program for it. That's pretty different from art, music, and film criticism, to name three.
That said, good food criticism is more than just expressing personal preferences, I think. I favor critics who are persuasive, well-informed, factually accurate, and compelling writers. After that, it's mostly about trust in their freedom from unfair biases and a sense of shared sensibilities, the feeling that we tend to like and dislike the same sorts of places. That last part eliminates anonymous reviewers, since you can't figure out where a person is coming from if you don't have a body of their work to read.