Me? On average, I play through a game about 3 times. Here is why.
For me, the first playthrough is a learning experience. I learn all the mechanics of the game, play around with them a bit, figure out the structure of the missions and side missions and just where everything is and when it's unlocked, etc... basically, the first playthrough is just a prelude for the second playthrough.
The second playthrough is the best. After learning how to work the game in the first run, I now can balance the missions and content in any way I want. I can create a perfect content and time balance now that I know where everything is and when it is available. The second playthrough is where I spend the most time with the game, where I have the most patience.
Then, there is the third. The third playthrough is usually meant to be the least-serious "just screw and fuck around" playthrough. This is the playthrough that I take least seriously, as I am not trying to make it perfect like the second. This is also when I usually get tired of a game.
So, how many times do you usually play through a game?