We worship the Son of God, the maker of all things (John 1:3). He is God over all, blessed forever (Romans 9:5). His becoming Man is something none of us can understand, and I'm sure we never will. How could we understand the fullness of Godhead dwelling in Him bodily (Colossians 2:9)?
When I was growing up, I understood the Gospel very differently than I do now – which is probably a good thing, I should expect our understanding of the Gospel to change with age and experience – I thought of it as a sort of response on God's part, which isn't entirely wrong. But there came a day when I realized that God knew exactly what it would cost Him to declare that it would require blood to make atonement for a soul (Leviticus 17:10–11). God made that declaration knowing full well it would be the blood of Christ that would ultimately be the price.
Watchman Nee points out that the first type of Christ going into death for us in Scripture is presented before the Fall (Genesis 2:21–25; Ephesians 5:28–32). So there's at least one sense in which the Gospel is more than a response to sin. Christ's going into death for us is more than "just" a response to the Fall.
John's Gospel seems to shine a light on that: it doesn't really present Christ suffering for sins so much as it's the Son of God giving life to those who don't have it. And we see something fascinating when we compare John 5:24–29 and John 6:48–58. In John 5 we learn that the Son of God can give life to the dead "merely" by commanding it: the Son of God can call the dead from the grave. In John 6 we learn that the Son of Man can give life too, but it costs Him: He gives life by giving us His flesh to eat and His blood to drink.
Of course I don't mean that the Son of God and the Son of Man aren't the same Person. Of course they are the same Person (see John 5:25–27). But the point is that the Lord gives the Gospel appropriate to whichever title He is using. So when we think of Him as the Son of God, we see that there's nothing He can't do: He is God. But when we think of Him as Son of Man, then we see that He pays dearly for the life He gives us.
When the Lord discusses giving us His flesh to eat and His blood to drink, He tells us that He is the bread of life that came down from Heaven (John 6:35–51). And He makes the remarkable claim that He came down out of Heaven so that we may it eat and not die (John 6:50). It was to give us His flesh to be our food and His blood to be our drink that He came down from Heaven (John 6:50–51).
And this is, I suppose, the point of my rambling: the Son of God became the Son of Man in order to do the unthinkable and give us life at an incalculable cost to Himself. He knew what it would cost, and He came specifically for that purpose (cf. John 12:27).