God of War is not an RPG. Sure you play the role of someone, but then that means every game is an RPG right?
http://en.wikipedia.org/wiki/RPGs
Basically, RPGs are games that have experience points, a level-up system, lots of different weapons and items. You usually run around in a level and will come across an enemy and you will switch to a fighting mode. They are usually turn-based. You attack then your opponets attack as well. You don't actually attack for them, you just choose what to attack and they do it for you...
Like Final Fantasy, Grandia, etc...