Love these type of collaborative articles! Everyone joining comes with a unique way of looking at the topic or question at hand :)
To see talks about immersiveness found through locations, gameplay, the accumulated effect of good design effects, a story that came at the perfect time, and even pacing... quite awesome and eye opening.
As for the Fallout 3, I completely know the feeling. Now that I think of it... imagine how immersive this game felt to me, after playing the original Fallouts 1&2 and immersing myself in them for about 1.5 years xD. I was a complete fan. No stone was left unturned on those pixelated and isometric maps.
And when I opened Fallout 3 for the first time, seeing all that I have only imagined as a kid, how it would look like from a First Person perspective, how the Vaults would've looked when they were not missing a water-chip, when I entered the first market store (Super-Duper Mart)... I got shivers.
It is a real joy to see proper sequels made to real old classic games, that we many times, played more with our imagination that relying on good graphics to see the world.