According to Bultman, Greeks did not see any reason to be grateful for their existence (see Bultman’s essay, “God and Man in the Old Testament”, Existence and Faith: Shorter Writings of Rudolf Bultman). There is truth in this statement, and there is also error. More precisely: the earlier Greeks did not see any reason to be grateful for their existence. By earlier I mean before Plato.
In Plato there is expressed a different tradition, having its start to the orphic teachings and the understanding that life in the other world was not just a shadow and caricature of this life, but a continuation, even more intense and real than this life.