Indeed, the thread title is simply incorrect. I suppose it could also be seen as offensive.
But anyway, there is a lot of evidence for the existence of Jesus the man, and most scholars of antiquity agree on his existence.
Jesus exists in several non-Christian sources, most importantly by the Roman historian Tacitus. Tacitus was writing about 50 years after the death of Jesus, and is believed to have had access to original source documents. The great thing about Tacitus is that he was a staunch Roman (ie. not sympathetic to Christianity) and he was also a very honest writer. Though he doesn't always state where his findings come from, what he does do is footnote himself to let the reader know when something is suspect, or without proof. He parts on Christ have no such footnotes, and are thus viewed as accurate and confirmed by himself.
He confirms the existence of Jesus, and also confirms that Jesus was crucified by order of Pontius Pilat.
Jesus is found in other non-Christian sources as well, so to say that there is "no proof what-so-ever" that Jesus existed is incorrect. There is plenty of proof.
As for God, that can be a tough one to crack for most. I think it depends on how you view existence.
Personally, I am a bit of a fan of Descartes on this front. Descartes shows existence through our ability to doubt. Essentially, he says that one can doubt their surroundings or physicality [ie. one might be in some dreaming, or drug induced state ... to give it a modern flare, one might be plugged into the Matrix

] So while one can doubt their physical existence, one cannot doubt that they are, in fact, doubting. That is to say, I must exist if I am able to doubt my existence. Or as the common way of saying it goes: "I think, therefore I am."
I generally apply a reverse approach to existence when it comes to God, in that the mere thought of God manifests its existence. In a Cartesian sense, you can doubt god... but you cannot doubt that you are doubting God.
God very much exists for many people in the world. Have a look at images or video of Mecca, and you will see thousands upon thousands of believers simultaneously praying. Have a look around a hospital, and see people praying that their loved ones get better. Take a look at Martyrs who were willing to die for their beliefs. Several people on this thread have also made testament to their beliefs. To those people, there is no doubt in the existence of God. God is, therefore, real.
Now... is there some being or power? Who knows. I don't think so, but it doesn't matter... the fact that people believe in God makes God real. If you doubt the reality of a belief, try to calm a child who believes the Boogieman will come get him at night. The Boogieman is very real. And this brings us back to Descarte, I suppose, who shows us that the mind is a very powerful source of reality.
Meh. Just my take on it.