Christopher Hitchens accuses Christians of creating make-believe characters. Belief in God is like believing in leprechauns. Theism and leprechauns violate Occam's Razor, a kind of general principle that entities ought not be multiplies in explanations, at least none beyond what is necessary for the explanation. Hitchens is confident that materialism explains the universe; thus God is unnecessary, just as leprechauns. However, he's incorrect that materialism adequately explains the universe; and he's also wrong that God has no explanatory power. God isn't like leprechauns because these little green men don't explain anything.
Materialism can't account for the beginning of the universe or morality, two major questions crying for explanation. Various naturalistic theories attempt to get at the cause of the universe, how something came from nothing, but no theory is an adequate explanation and is actually philosophically unfeasible. Effects need causes and God is a reasonable and adequate cause for the beginning of the universe. William Lane Craig has advanced this argument best in the Kalam Cosmological Argument.
Morality is an unnatural, meaning nonmaterial, feature of the physical world. Just for starters, moralities universality and incumbency just find adequate explanations in science. The Moral Argument for God's existence has been advanced for centuries and scientific progress hasn't antiquated it.Occam's Razor advises us to keep explanations simple. But it also guides us to multiply entities necessary to explain a phenomenon. Materialism is too simple because it fails to explain all that needs explanation. Leprechauns don't fill that role, but God does.