In season 5 episode 2 of Red Dwarf, Lister and his gang encounter The Inquisitor, a strange, extremely judgemental creature who believes it is his job to decide who has lived a worthy life, and who should be erased from history, replaced with someone who never got the chance to live. But the Inquisitor does not use his own standards to judge people. Instead, he sits down, he lifts his mask, and the one being judged will see their own face staring back at them. They are judged by their own confessions.
Much like the Inquisitor, God judges us by our own standards. Not in the sense that if we think we deserve Heaven, we get it regardless, but in the sense that all of us know we don't deserve it. The phrase "nobody's perfect" persists even in the secular world, and it's correct. Nobody is perfect. We have all sinned, and we all know it.
In our daily lives, we make a series of moral decisions. This is because we all know, even without knowing, that there is such a thing as good and evil. When we do good without being told that we need to, we show that we are already aware of God's laws. And when we try to cover up our evil, or hesitate before doing it, we show the same. We don't even need the Bible for this. The Bible only adds to the knowledge we already have of God, and unfortunately only intensifies the severity of the punishment for rebelling against Him.
This is one of many reasons we need to get the Gospel out there. No one can plead ignorance because no one is ignorant. No one will be able to stand before God and claim to be a good person. We need to point people to the good man who stood before God as a bad person.