I love this question, because its humble, searching, sincere. Why does God want our praise? He, or any deity, is far far above it. Why go through all this trouble creating this elaborate mess just to talk to a bunch of specks of protein. None of it, none of Christianity made sense to me. The purpose behind it all. Its just stupid.

But there it was in Ephesians 2:7, God's reason. I was relieved because it is a selfish reason. I couldn't stand the idea that God is just love love love... it was just giving and getting nothing in return. And it didn't reflect the Jehova of the Old Testament. But Ephesians says he did it for the glory. Who's going to be the witness of that? What peer-group or other beings would God point to and say "There I did it, I'm amazing."? I have no clue. However, this is so refreshing to me, because it shows that God is possessive and jealous, and very much like us, who were "made in his image".

But, I have to agree with agnostics... humans are far from the center of the universe. God is. Its his game. His strange, fearsome, terrible, wonderful work.

To break it down: God is completely pure (without sin). To be with God (which is what we would call 'salvation') we would also need to be without sin. Obviously, no human is without sin - meaning we could never be with God. Prior to Jesus, we were required to sacrifice things in order to atone for our sins and get right with God. Jesus provided an eternal, perfect sacrifice to pay for everyone's sins. It isn't so much that we need to worship Him, more that we need to accept the sacrifice He has already provided - if we reject the sacrifice, the full penance for all our actions is on us, and we can never be with God.