The 6th and 7th of the Rambam's 13 principles of faith (*ikkarim*) are:

6. God revealed Himself through the prophets
7. Moses was the greatest of prophets

Why the 7th as a separate principle?  The Rambam himself gives four reasons:

-God did not speak to the other prophets face to face.  
-God spoke to them in their sleep or when they were in a trance, not in broad daylight.  
-When God would speak to them they would lose their faculties because of the intense experience [Dan. 10:8ff, 10:16].  
-They could not communicate with God whenever they wanted to.  

None of this applied to Moses.

That's all well and good, but I still don't see how it adds to what Jews believe.  With the same logic, you could spell out what the Messiah will do, what the World to Come will imply, etc.  Why is that 7th principle there, instead of subsuming it in the 6th?