The question itself is flawed. From a Religious aspect the whole concept of faith suggests an uncertainty of God's existence. If people knew that God existed, it wouldn't be faith. So when a religious person claims that God exists, they're simply saying the believe God exists, though they don't know for sure. By calling it "faith" it acknowledges a lack of actually knowing.
From a scientific aspect its impossible to prove or disprove the existence of God through scientific experimentation and therefore science has no ability to address the question of whether or not God exists.
So given on the fundamental basis for both Science and Religion, neither one can answer the question of whether God exists.
So really, the best answer to the question regardless of what your perspective is, is maybe.
