I need a problem to solve. The game doesn’t need to be hard. But it must require me to apply the scientific method: when faced with a problem, to postulate a hypothesis, to experiment, and to evaluate the results.
It’s not fun when the answer to all of a game’s challenges is to simply “git good” or to grind for better gear and try again.
It’s fun when the answer is to find out which skills to use, what is the right gear for each specific situation.
The best definition of what makes an engaging game is still the one put forward by Sid Meyer: ”a series of meaningful choices.”
When progression in a game is only about muscle memory, or grinding to level up a character, these are not meaningful choices. That’s just padding.
A meaningful choice is made by trying out differently-weighted gear in Dark Souls to get a better roll and faster sprint when facing the Capra Demon. It is to try out standing your ground in various positions in the arena, so as to find out the best spot to avoid being flanked or attacked from behind.
A meaningful choice is made by trying to optimize the equipment, the talent selection, and the sequence in which you use your character’s skills when playing one of World of Warcraft’s or Diablo III’s classes – and yes, you can check out the “ideal” combinations on a site, but what is ideal for the prototypical player may not map well to your style of play. The decision remains yours.
A problem to solve, and the possibility of experimenting with different paths to reach the solution; that’s the difference between a game and a time-waster.