The main arguments for Gods existance seem to be..
#1 Look at the beauty of the earth, universe. How can you witness these things and not believe?
*many other religions make exactly the same claim. Why is your one special? Surely the beauty is therefore equally valid proof of the existence of hundreds of other gods? One supernatural explanation is just as valid as any other.
* Unfortunately, everything you describe can also be explained in mundane, rational, scientific terms, without the need to invoke a Creator.
* What about the nasty things in life? Guinea worms, anthrax, mosquitoes; all the blood-sucking, parasitical, disease-bearing, poisonous beasties that kill us and each other in horrific ways?
#2 Six hundred million people follow my religion. They can't all be wrong - there must be something in it.
* Nine hundred million people follow religion Z. Are they all wrong? Truth is not democratic - you can't vote for objective reality.
* Maybe they are right. Maybe their god exists as well as your god?
* If they're wrong, couldn't you also be wrong? After all, they seem to believe at least as strongly and sincerely as you do, and for many of the same reasons...
#3 "I have personally witnessed a miracle. I can trust my senses."
* Lots of people have personally witnessed Elvis working at the Drive-Thru. Should I believe them also? Without any sort of evidence, personal subjective testimony is not very convincing.
* Many people from other religions claim to have witnessed miracles. Does this mean that their God also exists? Just how many Gods are there?
* Are you positive that Divine Intervention is the only possible explanation for what you saw?
#4 "My God is a living God. All those other ones are just ancient myths."
* Those gods were "living Gods" to the people who believed in them. Zeuss, Odin and Jupiter once had followers every bit as devout as you.
* Many of the "ancient" religions still have active, devout, sincere followers. Just like you. Why should I accept your claims over theirs identical ones?
* How many people claim to worship dead gods?
#5 "We are God's Chosen People."
* So why doesn't he look after you a bit better? How many of his followers have suffered or died recently? Statistically, are you any better off than followers of other religions?
* Again, the same claim is made by other religions. How do I know they aren't the Chosen Ones?
* So what are the rest of us here for? What about the ones living in remote villages who will live their entire lives without even hearing of your god?