Here are two points to your headline question:
There is a difference to the accounts in the Bible to fairy tales and myths. The first is that Bible make a myriad of historical references, many of which are provable. For example, Genesis 12 states that Abraham was from Ur of the Chaldees. You can go and look at the ruins of Ur today because it was discovered in the 1930s and yes, the Chaldees were a people in history. You can even make a historical case for Abraham being a person in history. But this does not mean you can prove that God exists or that God told Abraham to do this or that. But, it does mean that there is a historical element to the Bible that places it apart from fairy tales and myths.
My second point is without an intelligent designer, one is forced to believe that the universe was spontaneously generated. We now laugh at the idea of spontaneous generation this being disproved by Pasteur who opened up the whole field of micro biology over 100 years ago BUT it is now science to believe that a whole Universe can spontaneously generate. What the athiest believes is that 'nothing' or an undefinable 'something' exploded and all the ingredients to make this Universe, including the ingredients necessary for life in all its complexity came into being. The natural selection of Darwinian evolution has proved to be an inadequate mechanism to generate new species and the later idea of mutuations being an adequate explanation, has been steadily eroded with the increased knowledge of genetics.
So, in summary. It makes a lot more sense scientifically to believe in an intelligent first cause for the Universe. For the Universe to explode into being without any cause sounds a lot more like a fairy tale to me.
Edit:
Respectively I suggest you read a wider range of sources. It sounds like you got your rebuttals from a skeptic. Nazareth was not founded 200AD...Mark is a reliable record and has not been altered...it was the first Gospel written. You say the Bible was tampered with from the beginnng: Give some examples. Please give some references in relation to Pilates words changing...I suspect that there are none. In regard to Clement...are you talking about Clement of Rome or Clement of Alexandria. I have read all of Clement of Rome's material but never seen this reference.
Edit 2:
Mark wrote first (tradition says he wrote as instructed by Peter). Matthew wrote second and there are some similiarities here. Luke opens his book up with this statement:
"1Many have undertaken to draw up an account of the things that have been fulfilled[a] among us, 2just as they were handed down to us by those who from the first were eyewitnesses and servants of the word. 3Therefore, since I myself have carefully investigated everything from the beginning, it seemed good also to me to write an orderly account for you, most excellent Theophilus, 4so that you may know the certainty of the things you have been taught."
Here he is freely acknowledging that he has other sources and he has spoken with eyewitnesses. What's the problem? He is an historian who is trying to accurately put together an accurate record of the life of Jesus.
It is also likely that Luke knew Mark personally (see 2 Timothy 4 written by Paul).
John wrote much later...probably in the 80's and his Gospel is nothing like the other three. (Interestingly, a portion of John;s Gospel is the oldest known manuscript of the NT being dated as early as 100AD...also interestingly this is the passage about Pilate's words :)). It is known as the Rylands fragment.
Have you ever read the Gospels? The consistency between them far outweighs the small inconsistencies, some of these being explained as a different viewpoint for a different audience (ie Jew vs Greek). But doesn't the small inconsistencies show that there was no collusion? If these writers knew each other (which I think they did) and they were making it up, there would be total agreement between the writings.
What 'critical ways' do the Gospels contradict each other? Why not give some examples.