He sacrificed himself as God incarnate. If he had just been a good man (even a perfect man) his sacrifice could only have benefited one sinner, not all the multitude of the redeemed portrayed in Revelation chapter 7. Only if he was both perfect man and perfect God could he be "the Lamb of God that takes away the sin of the world" (John 1:29).
Second critical point; Jesus did not come into existence with his birth on earth. He was the Word of God who was with God from the beginning, who is God, and who made everything that was made (John 1:1-3). So, what did he sacrifice?
What Jesus sacrificed was a sinless life. He gave up that sinless human life in order that sinful humans might be redeemed from their downward spiral of sin and death. Jesus need not have died, you see. He was without sin and could have lived forever on earth. He could have acquired monumental power because of that! He could have become ruler of the whole earth, if he'd so desired! All the wealth of the world could have been his to command. But he allowed himself to be handed over for crucifixion even though he had done nothing deserving of that (and Pilate knew it). He could have even come down off the cross as mockers challenged him to do. He chose to suffer to the death because that was the only way a once-for-all-time perfect sacrifice for sin could be made to God in heaven.
When Jesus died, the thick curtain in the Temple (separating the Holy Place from the Most Holy Place) was miraculously rent from the top down to the bottom. This showed that the way into God's very presence in heaven was now opened, and that Christ's sacrifice had been accepted. The symbolism for all of that is in the Old Testament but there isn't room here to go into it all.
Now, Jesus' sacrifice also included abasing himself to the point where he had to demonstrate faith in the promises of God. He knew he had been given authority from God to lay down his human life and to raise himself from the dead (John 10:18), but he first had to show he trusted in that promise of God by dying. Obedience had to come first. That's trust. That's faith. And when he was on the cross, having sin heaped on him like a ton of sewage, that faith was tested to the limit. When the Father forsook him (because God cannot look upon sin, and Christ BECAME sin on the cross), the holy, sinless Son of God knew what it was, personally, to be unclean and filthy in God's eyes. You and I cannot begin to imagine what that was like for the one who had been eternally with the Father and the Holy Spirit in the Godhead!
The sacrifice entailed the sinless One becoming sin although he had done no sin. That's what his sacrifice was all about - sacrificing his sinlessness without committing sin. It was necessary because none of us could ever do enough to pay for our own sin. Jesus paid for it all, by 'handing over' his perfect, sinless life to God and having faith that God would accept that as a legal satisfaction for divine justice. You see, if God just decided to forgive people without that, then Satan could accuse God of being unjust! Satan would be vindicated in his rebellion against God! It's a massive issue, and it all hinges on Jesus being God incarnate.
Only those who cannot see that it was God, in Christ, being humiliated and dying an agonising, undeserved death think the sacrifice at Calvary was no great thing.