These two verses declare that Israel is unequalled in greatness of two kinds:
1) They are unequalled in their privilege of calling to Hashem whenever they are in need;
2) And they are without equal in the world because of the righteous laws that Hashem has bestowed upon them.
Because of these two reasons, Israel is therefore the most important (”greatest”) nation. Two unequalled privileges are here pointed out. In the daily Shemoneh Esreh we say: “For You listen with compassion to the prayer of Your people Israel.” And here we see the source of this statement: “Who is such a great people that has G-d near to him as Hashem our G-d whenever we call out to Him.”
We are informed of a most exceptional status, that Hashem is most close to us and therefore grants His especial attention to the prayers of Israel.
In the following verse, we are informed of another unique privilege: “this Torah that I put before you today.” Although they are mentioned as two separate privileges (’For who is such a great people,” “And who is such a great people”), fundamentally they both stem from the fact that G-d is near to Israel. But this nearness is due to the Torah that they accepted, and which they loyally study and fulfill.
Thus the Torah study is declared as the chief service of Hashem: “The study of the Torah equals all of them.” (Peah 1:1) The greatest nearness is to think the same thoughts, and by learning His Torah one thinks Hashem’s thoughts. (Adapted from Fortune Nation)