The value of the diploma is directly linked to the value of the college. When you break it down a college diploma is only worth as much as the reputation of the college.
What about the education itself? Do the awesome professors actually teach? Are the social circles at the college going to lead the student where they want to go in life? What about potentially-burdensome loans at the end of it?
I think we need to get away from the idea of college admissions as a tournament with Harvard at the top. "Good" depends on many things and different students may best be served by different universities.
What is the purpose of college admissions -- to award a select few or to match students with colleges where they are most likely to succeed?