Rating systems suck, in general. Though they can be useful at times. Any form of entertainment or product has some form of rating system. Some rating systems can be helpful to know if something is worth their time and money. Then their are others ratings systems that you would wish you had a rating as to not waste your time.
Gaming, being a form of interactive entertainment makes it more subjective than any other form of entertainment. Due to this odd level of subjectivity it makes it more difficult to objectively judge a game since not everyone will have the same experience. Though when a game is legitimately good then its good but if its bad then its bad. Ratings systems can be useful for the games in between if you can find a reliable source for reviews. Now thanks to the internet there are just so many websites and YouTube channels that rate games. And each of them have their own bias and use a different method to rate games.
The most popular method to rate games, or anything, is with a number system. By using a number system people can easily quantify if something is good or bad without actually reading the review, instant gratification. Then there are those who mainly just critique the game like Ben “Yahtzee” Croshaw of Zero Punctuation or Angry Joe on YouTube. But they are in the minority. Most sites use a scale of 1-100, 1-10 or 1-5. An since I am a simple man I like simple things. So the 1-5 rating scale is the one I like the most. If a game gets a 4 or 5 then its worth a buy. If it gets a 3 then its probably worth a rent and below a 3 is garbage. Nice, simple and to the point.
Now the 1-100 scale and 1-10 are basically the same just scaled differently. These two scales can be very nit picky and sometimes want to give a game an exact rating. For some people this could be very useful if they are on the fence about a game. But I feel that rating systems are trying too hard when they need to give a rating of an 86 or 9.2. Personally I would like it if more sites would just have a simple scale of Buy, Rent, Skip. That way there would be no ambiguity if a game is worth playing.