GRE vs GMAT for entry into business schools

I recently read an article in the business week on how GRE is slowly gaining acceptance as an alternate exam for gaining entry into business schools, starting from Harvard business school. The article also mentions how it means that the monopoly which was held by GMAT is slowly being broken. But apart from those issues it also reminded me of an issue which has been lingering in my mind for quite some time now, on how valid are these tests from the perspective of attracting the right pool of students. We test them of basic Maths and their reading and written English and some interviews and group discussions to identify students who will go on to become successful managers. I think the sentence itself makes my the point quite clear ...

But then people might say that these exams have been quite successful till now, which is partially true, but the reasons may not be the test, but actually may be in spite of it. First, because of the fact that these tests are the known gateways, students may self-select themselves, (nothing to do with the test) and in the process we end up getting a pool of students who do well in business. And, we never know the results of an alternate way as we do not have one to compare with.

In fact at times i feel if it is the case of "Emperor's New Clothes" and all of us are happy with the way things are progressing. But maybe it is time that the larger issue of the need to identify newer ways of identifying students students who will do well in business be developed especially in the larger context of what is happening in the business world currently...