Most FPS are heavily scripted, short and even more linear than FF XIII. Pretty much like rail shooters.
Yes Deus Ex you could talk to NPC (and punch them) but from what I seen it still seemed dull. Same with Fallout 3 (too empty) Maybe taking a break between all the shooting like actual solders do from time to time and converse in the area you are stationed in free roam style.
Ever watch true war movies often times it isnt about rushin from point A to point B following your squad commander's orders like a lap dog. It is about being in the environment and taking care of your teammates and conversing with the townsfolk and sometimes being attacked by them or aided. The horrors that war inflicts on its casualties of the citizens and things of that nature. I guess developers are too scared to show that still.
I mean Fire Emblem has permadeath for years and no FPS does whats up with that? Like your actions resulting in teammates or civilians dying, teammates or civilians turning on you, women running up to you with a baby with a grenade undeneath it (okay maybe thats going too far).
So there really doesnt seem to be too much of that in FPS games. Most environments are desolate and abandoned already (No Russian doesn't really count that was just for shock value) and you have little choice in what to do (save for Far Cry 2 I think). Even Dead Island felt like a mess...
Metroid Prime is too empty. Barely any NPCs and you traverse the world by yourself like Fallout/Crysis.
Mass Effect is third person
Fallout is "empty" because its a desolate world and you basically traverse the world by yourself so there's little responsibility in your actions. This is why I brought up Fire Emblem. Your actions or lack of in Fire Emblem have a direct effect on your teammates
When you are a soldier you usually work with teammates.
For the most part the teammates in Call of Duty and Battlefield, Killzone etc are invincible until the forced script says otherwise. Not by your actions