"I don't read enough Arabic to make a judgment on whether someone could write a Suryah as impressive as one from the Qur'an."
I'm not someone with knowledge so If I make a mistake,don't get exited.
Allah,spw, has sent messangers to reveal his message for our purpose in life. If God exists, He doesn't create anything in vain,right?
This is a way in which you can tell,one way, to which religion is actually our obligation to our Lord,Exalted He be.
If you believe in God,you should have a reason to believe that God doesn't create in vain and that He would want us to live in a certain way.And that He would have told us,in some way, what our purpose is.
Through the scriptures, He has told us in what way he wants us to live, He reestablished the true path a few times.
The evidence that Muhammad,saws, is a messanger of God is the Qur'an. The Qur'an is Muhammad,saws, walking. It was in his brain,memorized. If you doubt that he was illiterate,well, I doubt that anyone was litterate at the time. There were no authors,books, television,schools...
Why would you be interested in writting. It simply wasn't used. It was unnecessary at the time.
We can proof through the chain of authority that the Qur'an is the original Qur'an.
I hope you understand what I am mean by a chain of authority. It's a chain of teachers. Like for example A taught B, B taught C, C taught D, D taught E, and so on and so on. With a book that is found in a cave, you cannot do anything because you cannot trace it back to the original author (A) . I hope this is clear, but if it's not, just ask.
We do not want to trace Scriptures to a cave, we want to trace them back to the Prophets(pbut). What we want is chain which says that Prophet X gave/taught his Book to his student who gave it to his student who gave it to his student 'til we arrive to a student who lives now.
This is used by historians in all fields and not just Islam.Don't you dare compare it to the telephone party game,pure ignorance.
Could Muhammad write the Qur'an. No, no one of the time could. Has anyone written a sura like that of the Qur'an IN ARABIC today? No....
Now it's up to you to do research:
http://www.miraclesof*************/index.php
jUST GO TO gOOGLE AND TYPE IN: mIRACLES OF THE qUR'AN.
Once you finish and read the Qur'an you can experience it's miraculous power. If you read it with an open heart and mind you might conversate with the creator of the heavens and the earth.