RPG is a game where you:
1. make important and story changing choices
2. your manual skills are mostly irrelevant for the outcome of battle
3. you develop your character or characters in great detail.
That's why stuff like Diablo isn't real RPG (no choices, extremly important manual skills), same goes for God of War (no choices, manual skill required, limited development of character) or for example Okami.
And then you get partial genres like jRPG which fullfill 2&3 but fail at point 1 or going ever further you get action RPG/hack&slash which mostly have point 3 but lack customizable story.
And Yes by that definition Fallout 3 is only FPS/RPG hybrid.
Oh and there's also sRPG genre which is some kind of console gaming naming weirdness as those games are pure strategy with character development. If someone tells me he is roleplaying wholo 50 guys and girls from Valkyria Chronicles I'll seriously laugh.
PROUD MEMBER OF THE PSP RPG FAN CLUB
