The thing is, as a game series, we're dropped into Kratos' story sort of at the start of his saga. We see him wage war against Ares, the Gods, and literally bring down Olympus and the entire pantheon itself.
We like the God of War Norse saga because we literally saw all of Kratos' development before are very eyes. We saw a man who, despite all his atrocities, was a father and husband desperate for forgiveness and redemption. So on that level, I can understand wanting to see the Greece saga first.
But the Norse saga is what's out right now, and it's the popular one.