Oh, FYI:
Fallout 3
I like Fallout 3 because of the sense of the desolate broken Wasteland that is on the verge of extinction. It's a shitty place and even if the populace has enough drinking water to survive, there's clearly too much radiation and not enough plant life to make the place anything other than a gravel-filled ruin and desert.
The Bedouin are able to survive in Saudi Arabia's desert but that doesn't mean that they'd not be better off in a greener regenerated land. Washington D.C. isn't naturally a desert so Project: Purity can do what the GECK is supposed to do and regenerate the land on a large-scale level.
The area is devastated by Raiders, slavers, mercenaries, and Super Mutants so that it is a hellhole with no stability. We can proceed to fight them off and in some cases wipe them clean off the map (and thankfully they stay clear). Like a Wasteland Lone Ranger you can rescue every settlement from one problem or another until the majority of them are taken care of. You can also exterminate the Paradise Falls slavers.
If you manage to get your Karma up to perfect and the level, the game will tell you that you've turned about things for the Wasteland. You can even bring the Brotherhood of Steel back from the brink as they're losing against the Super Mutants let alone the Super Mutants AND Enclave.
Decisions like, "Should I mercy kill Harold" or "should I put Harold's life before all the crops he's growing that can survive in the desert?" are ones that I felt had real weight to them. Yes, there's stupid quests like the Nuka Cola Challenge and the Ant-Agonizer (and Little Lamplight) but generally I enjoyed the balance of light with the dark.
I felt the atmosphere was also powerful because of Washington D.C. itself. Seeing the heart of the American Empire and the contrast between its stated ideals vs, the reality meant something to me. It may have been nonsense to you but there was something potent about seeing the place I'd been in real life and took tours of reduced to a ruin.
Can you rebuild America as it was? Should you? The Brotherhood of Steel are doing the right thing in WDC but are they? They've expended most of their lives trying to "fight for justice" and are losing because of it. The Outcasts may well be right that this just is not their fight.
I liked these questions a lot.
Is it political that gay people exist?