Who is right... Paul...? Or everybody else...?

I think that in the Old Testament, men were made righteous by their obedience and trust in God--like Noah, who believed God when He said it was going to rain, and was obedient to God by building the ark. In the New Testament it is pointed out that no matter how good we are, we cannot be "good enough" through our own works to enter the Kingdom of Heaven. We need a "sacrificial lamb" to atone for our sins. That Lamb was Christ. By believing and putting our trust in Him, we can be made righteous. The blood of Jesus covers all our sins.