I don't think Kryptos counts as a mystery. It is a riddle for sure, which isn't entirely solved yet, but it is as much a mystery as the final puzzle of Fez: We

I don't think Kryptos counts as a mystery. It is a riddle for sure, which isn't entirely solved yet, but it is as much a mystery as the final puzzle of Fez: We know exactly who made it, for what purpose, what it contains conceptually, and that the creator is even still alive. Voynich and the Money Pit are mysteries where none of these are true and many questions besides the solving procedure are still open. (Though, to be honest, i strongly suspect that Voynich is the same thing as Kryptos and the last Fez puzzle: An artifact straddling a weird line between riddle and troll.)