Here is some interesting math I did myself. A rough estimate of the amount of gods humans have believed in is about:
1.02 x 10^11
This is based on the amount of Homo Sapiens that have ever lived.(as everyone has an individual view of God) Because some people believe in multiple gods, this is really a lower limit.
This means that the probability of Pascal's wager, concerning the monotheistic God, is one divided by the above number, or:
9.8039 x 10^-12
When you look at it this way, Pascal's wager is not a good idea in the mathematical sense.