It is hard, if not impossible to quantify how many degrees of reality exist between two different perceptions. Even if we take a simple example like the question "What time is it right now?" For many of us, the answer will be different because we live in different time zones and continents. So who would be right in that scenario? Even the rate at which time flows for each one of us is probably different, however minute that difference is. How fast you are moving and how high up you live (further away from Earth's gravity) affects the rate at which time flows for you.
We probably all have different definitions for what "God" is. @
Unyqe called it "the energy of the universe." What if my definition for "God" is water? You may present an argument that water doesn't fit some criteria and should not be considered "God", but you cannot make the argument (and win) that water does not exist.
The point I'm trying to make is: The answer to the question "Does God exist" is relative. It is possible that "God", based on some people's definitions, literally exists in reality for them if no one else.