From Valley of Vison: Humiliation
"Let me never forget that the heinousness of sin lies not so much in the nature of the sin committed, as in the greatness of the Person sinned against. "
This is so because all sin has its roots in the combination of pride/fear/unbelief, so in their nature they are the same. In that sense no sin is greater than another, but they are all equally great in that they are sins against a holy, gracious, infinite God.