Not many people, if any, believe that they are *very good.* The knowledge of good and evil allows us to see our flaws. Even the most psychologically damaged, believe down deep somewhere that they/we are flawed. There is nothing within our flesh, character, or intellect that can honestly conclude we are good. This is the main reason that we compare ourselves with others. It is done always in an attempt to justify ourselves. How many times have you heard someone tell you, "well, at least I don't do that!" The problem is, that no matter how good we are, we can always find someone who appears to be better. Notice I said *appears* to be better. I can guarantee you, that if you looked long enough, was around them enough, you would find that they are just as flawed as you are, and furthermore, that we all are flawed at the deepest level. This is precisely why God was in Christ reconciling the world to Himself, not counting their trespasses against them, and He has committed to us the word of reconciliation." But Paul goes on with this by saying that he made Jesus, who did not know sin, to be made sin on humanities behalf so that humanity might become the righteousness of God in Christ.
It should be obvious, that the reason for humanities main problem, was not being able to be sure about their goodness, and actually a sense of guilt. The reason for this was a lack of real faith in God's declaration in Genesis 1:31. Once receiving the knowledge of good and evil, humanity always had doubt. Jesus main mission was one of faith. As the last Adam, his faith would redeem humanity the same way in which the knowledge of good and evil brought about the doubt and separation. There are a couple of passages of scripture that explains this from Paul's point of view. The first one is Galatians 2:16 KJV "Knowing that a man is not justified by the works of the law, but by the faith of Jesus Christ, even we have believed in Jesus Christ, that we might be justified by the faith of Christ, and not by the works of the law: for by the works of the law shall no flesh be justified." Christ alone, as the last Adam, had faith in the Father.... particularly, faith that God saw Him as good. Another verse in which Paul gives the same thought is Philippians 3:9 KJV "And be found in him, not having mine own righteousness, which is of the law, but that which is through the faith of Christ, the righteousness which is of God by faith:" You can see here that we are justified by the *faith of Christ* and not faith in Christ.
This makes Romans 5:1 a lot more interesting. Since we were justified by the faith of Christ, it is only logical that it is Christ's faith that justified us with the Father. That is why 2Cor 5:18-19 is the perfect explanation of the gospel. It is also why imputed righteousness is so important. God raising Jesus from the grave, brings assurance that we are indeed justified, made right, by Jesus Christ. Again I plead, be reconciled to God!