People play games for different reasons; some play to have fun, others do it for a sense of achievement, and for some it's for escapism. However, there are some games that if you spend enough time playing them, you'll start to notice that other games seem easier. Sometimes it's because the general difficulty rating is higher, though in other cases it's due to game mechanics giving you a different outlook on gaming.
For anyone who has instantly picked up Shadow of Mordor after having devoted hours into the Arkham games, you'll know what I mean. Despite this, I'll try to refrain from mentioning things like the Unreal Engine, as while playing these games will undoubtedly make you better at games with the same engine, it doesn't necessarily make you an overall better gamer.
No, this list will instead include the games that make you look at the gaming world differently, whether it's improving your gaming mechanics like aiming and reaction times, making you more cautious when navigating an enclosed area, or just helping you to think outside the box. So grab your controller, mouse, joystick or whatever you use for your recreational gaming time and jump into the world of player-defining games.