Here I will just address the christian god side of things, but the principles can be used for any god that has ever existed within the human brain.
Everything we know about god or jesus, we got from the bible. Without the bible, the jesus myth would have died out long ago.
The bible itself contains inferior knowledge to what we now know about our planet and solar system. Eg. the luminaries in genesis , one for day and one for night. We know the moon is not a source of light, it's a reflects it. Joshua asking for the sun to stand still and god did...the earth moves not the sun. The earth is not a circle but a sphere, and the hebrew language had a word for sphere, which was duwr (ball - a ball is always a sphere without exception), but in the bible the word used is chuwg (which is a circle like in a compass or coin). The history of the israelites is fictitious and emormous embellishments. That's only a couple of things in the old testament which show there was no divine direction in the writing - not even mentioning the laws.
Jesus is a different ball game in the fact that there is not one shred of contemporary physical evidence of his existence. The gospels are not a witness to him as they were written decades after his supposed death and historians and scholars have no idea who wrote them. The gospels didn't exist during the alleged life of Jesus nor did any of the authors make the claim to have met an earthly jesus. The gospels are nothing but hearsay and cannot be used as any form of evidence of truth. Also the fact that the gospels were written almost virtually in the thrid person. People who wish to portray themselves as eyewtinesses will write in the first person. Many of the passages attributed the jesus were the invention of the authors as many passages relate to things said when he was alone and even thought, the same techniques that fictional writers used. At best the gospels are hearsay, and at worst, as fictional, mythological, or falsified stories.
There is not one contemporary extra biblical account of jesus to be found anywhere. Jesus was apparently famous throughout the region, by preists, roman governor pilate, even herod. Yet no one even mentions a thing. No preaching, no trouble maker causing problems, no trial, no execution, no eclipse, no earthquake. Nothing outside the bible.
The "evidence" believers use for the existence of jesus is even less credible than the "evidence" the ancient greeks had for believing in Hercules, yet Hercules is dismissed. Hercules had a lot more written about him than jesus ever did. So why the double standard? It doesn't make sense.
When it comes to god(s), people believe what they want to believe and their god is whatever they want him, her or it to be. No evidence required, just what they feel and interperet. There was actually a study done using an mri machine I think, I wish I could find it now, but they did a study on the god part of the brain, but asking people what god wanted of them, and the part of the brain that is active during asking and answering that question, is the same part of the brain that is active when asking what they themselves want. Just a little extra info.
I think I've rambled on enough. I could go on more but this is just a small part of the reason I now find it completely illogical to believe in any god without real demonstrable evidence, same with santa, dragons, mermaids, medusa, fairies, unicorns.