In 'The God Delusion', Dawkins writes: "I have found it an amusing strategy, when asked whether I am an atheist, to point out that the questioner is also an atheist when considering Zeus, Apollo, Amon Ra, Mithras, Baal, Thor, Wotan, the Golden Calf and the Flying Spaghetti Monster. I just go one god further." (p77 of my copy)
This is a philosophical error, a category mistake. The Christian God is not the same sort of thing as the other gods listed (assuming the FSM counts as such). So it's a little like having an orange in your pocket, and a man comes along and says 'you haven't got an apple in your pocket'. 'No, I haven't, nor would I claim to have'. Then you produce the orange and he says 'see, no apple!'
One of the great breakthroughs in Hebrew theology, a transition - an evolution! - that is documented in the Old Testament, comes when the people of Israel, in the context of the destruction of Jerusalem c. 586BC, realise that the god they have been worshipping isn't just the tribal God of Israel, which would be a god listable with all the others in Dawkins' text. They see their God as being in charge of all things, creator of all things, not just the Israelites. This conceptual innovation led to an immense shift in their theology - a theology that can be tracked in Scripture in all sorts of different ways. It was responsible, for example, for the writing of Genesis chapter 1, which articulated this idea of God as the creator of all things.
So it would be fair to say that, since approximately the sixth century BC, the Judaeo-Christian tradition (and the Islamic offshoot) hasn't believed in the sort of God that Dawkins lists. It's a pity that Dawkins doesn't take this into account in his diatribe, but that would take genuine intellectual curiosity.
NB please note that it is no defence of Dawkins' argument to say that 'the Christian God doesn't exist either!' (which is simply saying 'you have no orange in your pocket', a different claim to 'you have no apple in your pocket'.). The point is simply about what Christians are believing in - and that isn't what Dawkins is criticising. Hence the error.