Maybe I'm overcomplicating this stuff, but I have been reading about "D1" through "D30" numbers where developers track how many new players they get and how many they retain.
If people play your game one time and never come back.. you have a problem.. if you have a group of players who keep coming back over time, then you have something that might have potential.
I have used Google Analytics before in my most recent game. This is pretty good at showing events in the game but wasn't really sure this gives the right data that accurately reflects the D1-30 numbers. Is there something folks use to specifically track this kind of value?