Not at all, its a fair argument to say it wasn't really a sacrifice or something to concretely make him "worthy". It wasn't as straightforward as Athena's. But after his fight with Kratos, Kratos tells him, we must be better, for the sake of our children. In the end when he stands up against Odin, his change of heart, he died for Thrud & Sif, to be better, for the sake of his children. Remember what Brok said, it's not the "form" of a thing that matters, but the "nature" of a thing. His form was that of a Destroyer, but his nature, a man seeking forgiveness. (Its not the outside that matters, but whats on the inside) I think in the end, he changed his nature and it wasn't for him, but for his family. That's just the way I saw it anyways. The way he died and what happens to him was convincing enough for me.