Hitchens, in my estimation, suffers from exactly the same kind of logical flaw that many believers do: his nonbelief seems to be based more on his desire for God not to exist (because God is, in his opinion, the ultimate arbitrary dictator who can violate our innermost privacy and convict us of thought-crimes) than on sound ontological or epistemic arguments. Believers, of course, make the same mistake of concluding that because they want God to exist, he actually does. But wishful thinking says more about the wisher than the wish, either way.
Where I do think Hitchens has made substantial contributions is on his critique of religion, religious morality and the religious instinct. It's his moral and historical arguments, and not any ontological claims, where I think he has a lot of interesting things to say. And if nothing else, he has that rare gift of helping us to think about many ideas, that we tend to take for granted, from refreshingly and interesting new angles, as the following excerpts show:
Cheers, Hitch!