Say there were no Bible, no Qur'an, no Bhagavad Gita, no religious texts of any sort. How would we know just by examining the world around us that there is a God?
I think the fact that there is, to some extent, some order to the universe in the form of natural laws, such as gravity, is where people would place there bets. It is commonly believed that some form, some shape of order exists. If this is true then there might be someone, most often believed to be some kind of human-God, that is presiding, and, possibly, intervening, in the universe.
That is where I think most "God-fearing" people would place there bets.
For myself, I would approach this question by asking what differences might exist between a world created by God and another world that came about in the absence of a God.
I think this question rests entirely on what your defintion of God is.
Which would be expected to have more wars, more prejudice, more disease, more disasters? Certainly we seem to have enough of these to suspect the possibility of an absence of God in this world.
Again, this depends on what your defintion of God is. If your definition of God lies similar to the God of Shiva, then the wars, prejudice, disease, and disasters might be used as evidence that this particular God exists.
Shiva - Wikipedia