There are many qualities that make a good game, although this does not always mean you will like it, because everyone is individual in their tastes. For me, being a gamer myself outside of work and business there are a few main qualities I look for in any game - Graphical Quality/stability - how good the game looks and feels and also how quickly the textures load. Progression - A good game needs a storyline/a progression so that when playing it you don't feel like what you're doing is unhelpful to your game progress or even 'pointless' Fun - A game can be the most well designed and built game in history but if it is a game where you walk around in a circle in an empty room, that's going to be boring! Compatibility/stability of the game - When you start committing your time to a game it is important that you know this game isn't simply going to disappear anywhere or fall through, otherwise the time you do put into it will not only be wasted but leave you feeling regret .
I check game by screenshots, game-plays and comments about the game by those who have finished playing it.
Most games are good. Strategies as for example help think widely. The only thing is not to play too much.
Easily enough. You can talk to friends (if you have friends that play games) Or you can view reviews on websites to see the general gist. But obviously to get your own opinion on something you need to experience it. So playing it yourself would determine whether you like it or not. Everyone is different with their opinions.