Standard: cheating, lying, stealing etc. I don't believe not believing in god is a sin.
You have never stolen? Never been selfish or covetous or greedy? Never been drunk? Never failed to lover the Lord thy God with all your heart, mind, and soul and your neighbor as yourself? You have never lied? Never cheated? Never hated or been angry without just cause?
Unbelief is listed as a sin but there are plenty more that make a man just as guilty of rebelling against God.
Romans 1:18-32