There is every bit as much evidence to believe that the Greek Gods do exist and are responsible for the creation of the Earth as there is for any other God - perhaps more so.

I like this argument for the existence of more than one God -

1 Gazelles are perfectly designed for running away from lions.
2 Lions are perfectly designed for chasing gazelles.
3 This design cannot happen by chance.
4 Therefore, the design of lions and gazelles must be the result of intervention by an intelligent agent.
5 Gazelles and lions are each designed to thwart the design of the other (from 1 and 2)
7 Therefore, gazelles and lions had seperate designers competing against one another.
8 Grapes are perfectly designed to be useful to make wine out of.
9 What has this to do with gazelles and lions?
10 Therefore, there was yet another designer who made grapes.
11 Therefore, Dionysus.
12 There are also lots of other designers (from 7)
13 Therefore, the rest of the Olympian gods exist.