Kratos is a character based on emotion. He's not supposed to be all complex and stuff. Revenge and hate drives him. That's it. A lot of people may like him cuz he's "bad ass" and "macho" but if you've ever felt strong emotions of hate or anger or revenge that was rooted in lost love, only then can you really appreciate the character of Kratos. And he embodies those emotions just perfectly.
As for the storyline, it too is based on emotion and it is one of the best in video games. The symbolism of having to fight off an army of clones of himself to save his family was amazing stuff. That's poetry in a video game. Being stained with the ashes of your family is powerful stuff. But because it's a video game it is kind of looked at with an eye of immaturity compared to movies or books.