+1, Fallout 3 was really the first time we really got to see things like that that would really hit you on a deep level in the Fallout world. Remember the radio signal from the father who was broadcasting from the drainage pipe trying to get someone to come and help his sick son who was dying, then when you get there all you find is a childs skeleton on the bed with two advlt skeletons lying beside it? I was really hoping when you found them you would get a quest to go find medicine or something to help him, but it was alreadt too late.
There were a lot of moments... no, not just moments... often long periods of time, sometimes... while playing FO3, that I felt alone. Vastly, utterly, alone. And awed by the gameworld around me, and its reminder of what could have been, or could yet be. And alive- a feeling would seep into you over time, as you explored things you had never seen before in the gameworld, in desolate, frightening, terrible places... and places strangely beautiful for their raw unnatural desolation and danger- you felt a thrill of being alive, when so much life was dead and gone and forgotten. This at the same time as the loneliness deep down in your bones... and for the same reasons.
I've seldom been moved by a gameworld I've played in over the years, but FO3 did it in spades. Fear, sadness, loneliness, and the primal joy of surviving it all and learning to become the baddest mother reaper in the Valley of the Shadow. Yep. Talk about 'that indescribable something' that sets some games apart...