Basically to compare the quality of different works in specific profession, one must ask the professionals of that field to express their opinions about them. For a better understanding we will refer the below example:

Imagine Dr. “A” claims to the whole wide world that no other Doctor is better than him and he is the best out of all doctors. Now imagine that his argument is against others, and so they want to prove that he is arguing in vain, therefore:

1) If no Doctor claims that he is better than Dr. A then it is clear that Dr. A was right.

2) If Dr. “B” says that what Dr. A has done is wrong and that he will prove that he is better than him, then those who are not familiar with the medical profession cannot judge nor distinguish the two Doctors.

Now about the miraculous character of the holy Quran, we can say that

since no one was able to give a proper answer (making a verse) which can be also approved by Arabic literatures, it is proven that the Quran is a miracle even to those people who do not know anything about the Arabic literature.

 Yet if someone has claimed to challenge the Quranthey must have had the approval and confirmation of Arab literalists.