It's not the crucifixion that makes Jesus' suffering so extraordinary. It is that in his crucifixion he bore all humanity's sin and suffering. This is where his torture was singularly unique. This is why he sweat blood. This is why no man can ever identify with his suffering. In this Holy Week, consider an excerpt Martin Luther:
On His soul lay the sins of the whole world. The death he had to suffer was a death caused by sin and imposed by the wrath of God. For since he had stepped into our place, had taken our sins upon himself, and had ventured to render satisfaction for them, he felt both at once, the sins of the whole world and then the death he had to suffer for the sake of these sins.
Therefore we are not only unable sufficiently to speak of this suffering and anguish, but we are also unable to think of it sufficiently. All the anguish and fear of all other human beings are, by comparison, much, much too slight, because the sins of the whole world are resting on him alone. He is to pay for them with his death, whereas everyone of us has only his own sin resting on him.
Yes, human suffering is slight when compared with that of this Man: all the world's sins - sins committed from the time of the first human being, Adam, until Judgement Day - burden the back of this one Man.