Why has there not been a game that tried to actually try the Fallout route? Particularly the reactivity.
To date, there are still only 3 games that gave importance to player reactivity:
>Arcanum
>Fallout
>Fallout 2

In these 3 games, the world reacts, at a minimum, to your character's intelligence. If you have a low int character, NPCs will treat your character like an idiot, mostly to humorous effect. Now this is mostly flavor-text, but beyond just low-int dialog, the world actually reacted to your actions and choices.

Fallout 1
>if you were careless to who you divulged the location of Vault 13, the timer would lessen.
>killing children will get you branded as a child killer
>multiple ways to approach quests

Arcanum
>some quests are different depending on who you have on your party and who you kill
>what you do is reflected in Tarant's newspaper
>multiple ways to approach quests