Here is a typical discussion you'll find on the internet about a review of a game.
A: This review sucks, because X.But C isn't stupid. C is right. If you write a review, you are not just giving an opinion. You are giving a judgement, and a judgement is something that aims to be reasonable and objective. There are standards to which a judgement must conform; and a judgement can fail to conform to those standards and be wrong.
B: A review is just an opinion, man! It can't be wrong or right.
C: No, a review is not just an opinion.
D, E, F, G and H: You're really stupid!
It is important to understand that this reasonableness and objectivity have little to do with the final verdict expressed in the judgement. Reasonable judges can give the same game a 10 or a 3. A judgement is reasonable and objective when it is based on reason; when the judge can give an analysis of the game and explain his verdict using criteria that other people can understand and sympathise with. There may be disagreements about the exact application of those criteria, but there is in general agreement about the criteria themselves.
Why was this topic in the back of my mind for a long time? Because every IF competition has a couple of judges who flagrantly ignore the basics of what it means to be a judge. These are the people who write reviews that go: "After playing for five minutes, I really didn't like the game and I couldn't be bothered to play any further. So that is a solid 1." That is not a judgement about the quality of the game. That is an expression of personal feeling. There is nothing wrong with approaching IF with the idea that you will stop playing any game that doesn't make you enthusiastic in five minutes. Fine. But something is very wrong with having this attitude and then being a judge in a competition. When a competition is looking for judges, it is looking for judges, for people who are willing to invest enough time and thought into the games that they can form a reasonable judgement about its quality; it is not looking for people who believe that their immediate emotional reaction to something is valid and worthy of being communicated to the rest of mankind. (This may be hard to grasp in the era of Facebook and Twitter, but really, it is true!) If that is the way you approach a competition, you are just as wrong as a legal judge who doesn't weigh the evidence but bases his verdict on personal like or dislike of the accused -- the only difference being that the consequences of your actions are less dire.
So, yes, reviews can be reasonable or unreasonable; they are not just opinions; and judging a competition is serious business. Before you give a bad mark to a game because you "didn't like it", ask yourself whether you have seen enough of the game to come to a reasonable judgement. Otherwise, a little bunny cries. Really.