The perfect God argument has got a formal name, I cant remember it at the moment.. Ontological Argument.
Guanilo, put forward a critique that goes like this...
I imagine a perfect island
It has monkey butlers, a rope swing, unlimited coconuts and it exists.
Obviously the problem with the ontological argument and the island argument is you cannot just add existence to a list of requirements for a perfect island, wikipedia is a good source of info on the subject.
Also it uses language to prove God, and this is dodgey in the extreme because applying our language to God in the first place is hard.
Wikipedia info
Ontological argument - Wikipedia, the free encyclopedia
I prefer the design argument - the chance of the Earth existing in the correct conditions for us and other animals to live is (1/2)^6000000
or 6 million coins all landing heads up, is it really possible that that chance happened?