Im an agnostic atheist but am really interested in religion, so I would apreciate any feedback on my musings.
From what I understand of Christianity, the central (not sole) principal of worshipping christ I that he sacrificed himself for us and our sins.
What I don't understand is that; many people have sacrificed themselves for greater causes in our history - why shouldn't we worship them?
Imo, the only good reason for worshipping anyone is that they are worthy of being worshipped.
Our Lord is worthy of being worshipped because of who he is, not because of what he did. With or without the Incarnation, God is worthy of our worship because he is the Creator of all that is, seen and unseen, and the author of our life. With the Incarnation, he is doubly worthy, because he has provided for us a bridge which reaches between heaven and earth.
If you consider Judaism and Islam, they both take the same approach to God. God is seen as beyond our reach, beyond our understanding. He cannot be contained or defined, and whatever we say of him will always be inadequate, however hard we try. God is very much God, in other words.
In Christianity we have a radically different perspective. We have that same God; unknowable, unfathomable, ineffable, deciding to have mercy on creatures which sometimes try to do the right thing but often fail to manage it because we either do not understand him, or do not understand ourselves. God did not have to try to reach us, but he did so out of love.
In Christ, God puts off his immortality to wrap himself in our mortality, and is born as a tiny child. He then lives our life; fully human, and prone to the same as we are, except that he had the willpower not to fall into sin. He was fully human and fully God, both at the same time, just as each one of us is fully, 100%, the child of our mother and fully, 100%, the child of our father, not half of each. Fully God and fully man is a description of identity and relationship, in other words.
As has already been said, there are different views on the Passion. My own view is that the Lord's death would have been equally substitutionary however it happened. His birth necessarily denoted that he would die at some point. In the event he suffered a death that for a Jew was considered particularly disgraceful, and which caused him immense suffering. It enables those who suffer today to find in God an understanding and an empathy that would not be possible if the Lord had died an easier death.
In his dying, the Lord lost touch with God; he fell into doubt, confusion and despair, and God allowed this. There is no human emotion; no pain, no loss, no suffering, that the Lord did not suffer with us.
Having died, Christ rose again, not for his own sake, but for ours. He could have gone straight to eternity, but he chose to return to show us where the bridge is to be found; in belief in him. The cross is the bridge by which mankind can find God, and in finding God, find eternity.
In short, God exchanged his immortality for our mortality, so that through him we could exchange our mortality for his immortality. This is what is known as the Unequal Exchange. And this, imo, is the reason for the Incarnation. Having gained immortality through Christ, our role is then to remain where we are, in the place he has called us to serve him, and to be his representatives to those around us. Many people have their own cross to bear in this life, but it is made easier by knowing that we do not do this on our own, and that we follow in the Lord's footsteps.
As for your last point, we should certainly honour the memory of those who lay down their lives so that others may have freedom; the Lord himself said that no man has greater love than to do this. But the Lord did not just lay down his life; he laid down his divinity and made himself subject to death for our sakes. He took our sins upon him, and bore them all, so that we can now take those same sins and failings and lay them at the foot of the cross, and be freed from their power over us.
I could certainly lay down my life for my faith, or for something I strongly believed in; I think most people could. I could not by doing so take away anyone else's sins or failings, or provide a bridge for them by which they might reach God.