Supposing we could exclude this risk. For example, we can say that collectively, the gospels are a "statement against interest", since multiple documents report that first century Christians were persecuted by Jews. It is quite certain that the authors believed what they said to be true. So that's the risk of lies excluded.
We also know that numerous documents corroborate the central claim that Jesus worked miracles and was raised from the dead. Letters by the church fathers, for example. Thus it is certain that what the four evangelists report cannot be described easily as "mistakes", since it is evident that many people believed they witnessed the events described.
So really the only credible argument left for the unbeliever is that Jesus himself was the most skillful magician ever, and tricked people into thinking he had healed people and himself been raised.
Yet if this was true, then he would also be deceitful in the extreme, and we would not expect to find the things we read about his character and morality, and that of his followers.
So believing the gospels does not seem unreasonable.