Kratos is a cinematic presence that deserves his own movie. Its actually very possible to make a great movie out of God of War, if one were to focus on the right elements.
Of course a movie couldn't faithfully adapt God of War 1, or else the only character the audience would see for most of the movie would be Kratos completing all of the necessary tasks that would lead him into battle with Ares. Which would be enough for me, but it wouldn't work in a movie sense.
Of course changes that avid fans such as you or I would find disappointing would have to be made, but I know it would be worth it just to see Kratos on the silver screen.
But to ask a question like that is pretty deep, one would have to wonder why do people have this innate desire to see their favorite game, novel, superhero transformed into a movie at all? Why can't we just be content with what we have, why must it always come down to "what if this were made into movie"? Honestly I don't have an answer for you, but I disagree with you as far as making GoW into a movie, it definitely would kick all kinds of ass (if done right, like everything else in life).
And besides, with all of these game's getting the greenlight to be made into movies, I figure I'd like to see my favorite one made into a movie as well. I mean, come on, Pac-Man is getting freaking movie? Why shouldn't the badass of all badasses get his movie made as well?