Should God have made his existence perfectly evident? Should he have?

Many of the things that it is supposed that God could have done to make his existence perfectly evident could be passed off as the work of powerful (but evolved) aliens. And no matter how much evidence God provides, there is some additional piece of evidence that an atheist could say God didn't provide, and if God really cared for us, he would have provided. The amount of evidence God could have provided has no intrinsic maximum.