Depenss on what you want. Strategy? EU4 - although expensive - is good. Civ 5 and/or 6 are a saver bet, cheaper and definitely fun.
Action? Can't really help here, I don't play action games.
Adventure? Papers, Please is great, although it only lasts 4 hours.
Simulator? Americe Truck simulator is currently on sale and definitely a good buy. Euro Truck simulator 2 is good too. Personally I'm currently enjoying Elite Dangerous - it's a truck simulator but with spaceships, space and combat.
Casual? Game Dev Tycoon is cheap and fun. It's also a bad game, but that doesn't really matter when you're having fun.
There are countless more games out there - good games, too. You just have to try them out to know which one's good for you