Just take a gander at Fallout 1. You're introduced to a land marred by nuclear war; a grim, desolate wasteland that holds uncertain dangers. Despite this, we see that humanity is starting to rebuild. People are once again forming communities based around common goals, and some semblance of an economy is starting to take shape as caravans roam the wastes. The world is still very much a hostile land, but beneath the sands lies a glimmer of hope for mankind.

Next we get to Fallout 2. The aforementioned communities have amalgamated to form a fledgling republic, a sovereign nation that has risen from the ashes of a once prosperous civilization. Shady Sands is now a sprawling hub, home to thousands of people.

Fallout 3 seems to have gone a different direction. The only semblance of optimism we get is with Project Purity, but otherwise we are presented with a land that has yet to recover from a war that happened 200 years earlier.

I hope Fallout 4 continues that theme from Fallout 2 (and New Vegas). From what I've seen, it seems to be going that direction. The ugly green-tint from Fallout 3 is replaced with a more vibrant color scheme, and a society has formed from the remnants of Boston.

With purified water being readily available and the east coast BoS hanging around I think the world is looking up at least.

Diamond city looks like an ok place to live and I'm sure living in the same area as MIT is a quality of life improvement, even if they don't share much the area is probably decently protected.

Fallout has never REALLY been optimistic.

Behind all that rebuilding is the constant theme of "War, war never changes" that humanity is doomed to destroy itself like it did in the past. We see this is the ever present racism, bigotry, and sin that consumed the old world being repeated in the new new.

The optimism is nothing but a smokescreen to cover the coming storm, which occurs in Lonesome Road, when Ulysses destroyed the new world with the weapons of the old.

Mankind CANNOT hold.

Funny that you use Lonesome Road as an example to support lack of optimism. I agree that the nuking obviously embodies all of the progress made being for nothing, but that's just one ending. And if you convince Ulysses otherwise, he'll admit he was wrong and take a considerably more optimistic view on whichever side you take. All of your dialogue with him throughout the dlc is basically you making an argument for your chosen faction, and it even gives you a chance to acknowledge its flaws first-hand, and explain why you think you can make it work despite those flaws.

And then there's the ending saying that "War never changes..." BUT "men do." And we can shape the wasteland into something good.

I'd say that, nukes aside, Lonesome Road can potentially have the most optimistic ending of any Fallout content to date.