Without God, there is no rational explanation for the universe, life, rationality, the laws of logic, or morality. So, although it is true that humans have invented many false gods, it remains that the existence of God is necessary, rationally speaking.
Some argue that it is likely that the Christian God is an invented God, and that Christians do not have any evidence that demonstrates that the Christian God is real. This is what Bill Flavell argues in his post, "Eight reasons Christianity is false":
There is clear evidence that humans invent gods. Humans have invented so many gods that the default assumption should be that a god is a supernatural entity invented by humans. Christianity would need solid evidence that the Jewish god is an exception to this rule but there is no such evidence.
Flavell says, "Humans have invented so many gods that the default assumption should be that a god is a supernatural entity invented by humans."
There are at least two problems with this assertion:
To read more about how the Christian worldview is a necessary presupposition for rationality and the laws of the logic, see Greg Bahnsen Debates Atheist Gordon Stein - Highlights