I rate software using five guidelines; “gameplay”, “sexual content”, “story”, “sound” and “visuals”. Each of these guidelines are divided into smaller sub-guidelines, which differ between genre and availability.
For example, I am more stringent on “story” when analyzing a visual novel than I would be if I were writing about sidescroller.
The final score (or “verdict”) is an average all of categories, when applicable.
Scores mean different things for different genres.
I don’t consider a “5/5” puzzle game to be a better game than say, a first-person shooter. In my opinion, it’s unfair to rate all software equally. What makes a puzzle game fun won’t apply to any other genre. In an effort to maintain an objective stance when I publish ratings, I only compare like-games when I deliberate scores.
I wouldn’t rate an RPG poorly because a visual novel doesn’t have any “grinding”.