In the perfect world there would be no reviews. With games specifically it’s rather easy to tell which ones are going to be good or bad. All you have to do is read the description to tell if the game is the genre that you like. Watch the gameplay videos and make sure that the game seems fluid and not choppy. If the game is choppy you should automatically be warry of the game. Either the developer did not take the time to polish the game or potentially the graphics are too powerful for the system.
One of the most important steps is to actually play the demo! Games are meant to be played. Your final judgement should always be based on the demo. Watching videos on the New Super Mario Bros is rather boring but when you sit down and play the game you’re probably playing the most fun video game in years.