I get the question “Is game X ok for my kid?” a lot, and while it I might have some knowledge about a game (and will gladly give you if I have an opinion). I know very little about what you think is ok and not ok for your kid.
First you should look at the ESRB, though this is usually to general to make an informed decision in my opinion. It is a good place to start. Also many smaller games like the ones you get on your phone and tablet will not have ESRB ratings. Getting an ESRB rating is a process and costs money…
Second go to Youtube and type in “Lets Play” X, where x is the name of the game. You should find videos of people playing the game, sometimes all the way from start to finish. They often have commentary. The commentary may not be kid safe even for kid games. Watching the Lets play does several things.
Lets you see what the game is really like when being played, and without having to buy it.
You can skip around the videos sampling the entire game without having to invest a lot of time.
You do not have to learn any game controls.
Here is an example search for lets play Shadow of Mordor, (ESRB M).