I wonder if you ever noticed this. Noah is not pronounced to be a just man, perfect in his generations and that he walked with God,until after God describes the wickedness of the times leading up to the Flood, and that Noah found grace in the eyes of the Lord before he ever was pronounced a just man.
A conclusion is inescapable: In order to be consistent with the rest of the Bible, Noah was not chosen by God because he was a righteous man, because he was not. He too was blindly involved in the pre-Flood wickedness. To what degree, I have no idea, and until God opened his eyes, until God took action, until God sent forth His Spirit, then Noah responded, and the rest, they say, is history.
Please consider how God looked at Noah with favor because he did what he had been prepared to do in faith, as we read in a correct translation of Genesis 6:8-9 from the Amplified Bible. Many have said this sets Noah apart perfect in his generations, but I think the Amplified has a pretty good here:
By faithfully living and learning God's way of life in whatever way God gives, we too become part of God's living witness of faith in the hope that is before us through the merciful and complete work of Jesus Christ.