I have two criteria to call something a game:

1) It must have set rules.
2) There must be an element of competition.

Now that word 'competition' is a bit vague. That doesn't mean you have to be playing against other people. It can also include trying to set goals you have set yourself, Competition was the closest word I could find for what I wanted to express there. Basically it must have goals or objectives.

Many people will tell you a game has to have a failure state. I disagree with that. If you decide to build a tower in Minecraft and don't finish it, have you failed at the game of Minecraft? I don't think so, you've merely adjusted your goal. To me, as long as you are setting yourself or being set a goal within a set of fixed rules, it can count as a game. "The floor is lava" is a game. "How many sheep can I count before I fall asleep?" is a game. The Order 1886... well, maybe not, but you catch my drift