Romans 2:13

For it is not those who hear the law who are righteous in God's sight, but it is those who obey the law who will be declared righteous.

(v13, NIV)

The point is that God shows no favoritism. This is with regards to judgment according to whether they do good or bad in a sense. Some may object with the fact that only the Jews were given the law, but nobody else was. In the last verse, Paul was trying to say that you will be judged according to the measure of truth you have been given. However, even those who are judged apart from the law will perish apart from the law. Here in verse 13, Paul takes his argument a step further to point out that the hearers of the law are not righteous in God's sight. So, just because the Jews have the Law doesn't mean that they are righteous. Rather, it is the doers of the law who will be declared righteous. It doesn't matter if you've heaped up a whole bunch of knowledge in your brain. Who cares if you've memorized the entire law, what matters is if you are a doer of the law. Paul will take this argument further in the next few verses, but the point remains that it doesn't matter that only the Jews were given the law.