Games, movies and books tend to be rated on a 1-10 scale, 7 being the lowest and 9 being the highest, as they say. Or 1-5 stars, which is pretty much the same. As a game reviewer, I've heard, you can expect a hard fight to get anything outside that 7-9 range published as your official score, if you work for a major outlet. If you don't work for a big publisher, then obviously you do what you like, so this post doesn't apply to you.
This 1-10 or star-rating scale is heavily skewed to the top end, is what I'm saying, and it's hard to decide what it means. Is an "8" game always better than a "7"? Probably not, if they're in different genres and you prefer one genre over another. It all depends on the reviewer's taste, their mood on the day, the rest of the audience (for movies or live shows) and so on. Some publications try to get around this "all in one" score by rating individual aspects for their reviews. For games, it might be "music", "sound", "graphics", "gameplay" and whatever else. For movies it would include "plot", "script", "performances" ... you get the idea. It's slightly more helpful, but still not objective.
I think it would be instructive to try a binary categorised rating system. For a set of aspects of the work, the reviewer answers "yes" or "no" and that's it. "Was the music enjoyable?", "Was the plot free of gaping holes?", "Did the movie/book/game feel too long?" Things like that. Now we have a way to break down enjoyment of a work and give it an honest score percentage (depending on how many "good" boxes it ticked). No mucking about saying "Well, I thought the music might have been a 3, maybe 3.5 stars, but I said that about that other movie last week, and this was better than that. Better make it 4". Just "Yes, music was good". It's still subjective, but it's harder to lie to yourself and worm around your answers if they're "yes/no" questions. Hopefully, if you ask the right questions, preferably across a broad sample of people, you'll get a representative rating, plus a solid data set to back it up.
Mokalus of Borg
PS - If you ask the right questions, this could work for a lot of situations.
PPS - And if you match answers with a user profile, the ratings can reflect the taste of individual readers.