Your algorythm would more correctly be written
((screen width()*screen height())*screen fps())*gameDuration
gameDuration of course holds the value of infinity which completely despoils the algorythm, up until that point a typical screen resolution of 1024x768 running at 60fps would yield the result: 47,185,920. For arguments sake we could take a typical gameplay duration as 8 hours and that is 1,358,954,496,000 possible games which factors onscreen display and any possible deviation of AI, control input etc.
Now there is one snag with all of this, did you stop to consider sound?
God created the world in 7 days, but we're still waiting for the patch.