God exists because we can imagine it

[robvalue]

You can say the concept of a god exists, as does the concept of anything we could possibly imagine. But there's no requirement that concepts map to anything real.

Defining what is real is a tricky business. In some ways, perception is reality, so to someone who believes the thing is real, it is real. The person will likely attribute various events to that imaginary being, and so to them, those events were really caused by that real being.

But if "what is real" is considered to be the "objective reality" that we all seem to share, then no, it's not real.

None of us actually experience reality, we live in the simulated interpretation our brains produce, based on an objective reality. Or possibly based on nothing at all; it's impossible to say which.