In my opinion, the GRE mostly checks how good you are as a test taker. None of that is important to academic success. It invariably filters for a fairly streamlined and optimized class of people, who have the money and time to invest into such a test.
The fact that the ETS seems to have a clear profit motive really rubs me in the wrong way. It is a private organization attaching itself to education and siphoning the money off students by selling their tests and training materials. Universities should design their own admissions tests and not rely on such parasitic entities.