I have to say that my experience has been that those who graduate from university with a high GPA are much more likely to make significant contributions to engineering. With the exception of those very few who are supernaturally gifted, most who earn the good grades worked hard to do so, and took pride in the accomplishment as well as in the challenge of achieving the grades. It is a form of competitiveness that carries over into a lifetime of engineering.
As such, I vote that GPA is usually a good indicator of liklihood of success. That is not the opposite of saying that a low GPA portends failure, because it does not. Let us dispense with the politically correct philosophy of trying not to hurt anyone's feelings and simply tell the truth.