Actually Egyptian is far from standard - the "j"
is pronoucned as "g," for example, leading to the
Najib/Naguib and Jamal/Gamal issue, and a lot of the words
used by Egyptians I know aren't even similar to the
Arabic we learn in class. Modern Standard Arabic is
classical Arabic, known as al-Fusha, that is actually based
off the Arabic of the Quran and generally understood
throughout the Arab world. Egyptian is the most widely
spoken dialect because most Arab-speakers live in Egypt,
and because of the dominance of the Egyptian
media.
Brian