The Fallout series has undergone a few significant changes over its lifespan. It's gone from an isometric turn-based experience to a first/third-person hybrid RPG to an open-world FPS to a live-service multiplayer game. Which game is the best is hotly debated, some may even say trying to pick which one is the best is futile, but I disagree.
Fallout 3 is the best Fallout game ever made. It's not New Vegas, it's not either of the originals, and it certainly isn't Fallout 76. I know there are things the other games do better than Fallout 3, but there's one perfect aspect of Fallout 3 that propels it above the rest: tone.
While every Fallout game does a great job of creating a sense of place, and truly set their scene, none do it as well as Fallout 3. That first moment you step out of Vault 101 and the sunlight fills your entire screen with radiant white light before the wasteland blurs into existence is one that is burned into my memory. It's one of the best parts about starting a new Fallout 3 run for me. The reason this moment is so good is because the game takes the time to give it meaning.
The opening hour or so of the game takes place entirely within the Vault - you play through several moments in your character's life, all crucial to their development and informing you of the world within the walls. Fallout 4 and New Vegas both have good openings, don't get me wrong, but I think they miss the mark a bit as they put you in the shoes of someone who already exists, rather than letting you create someone yourself. The Courier had goals and desires before getting betrayed, and the Sole Survivor has a whole family you only catch a glimpse of. Fallout 3 makes the character a part of you by having you experience key parts of their lives, seeing your crush getting bullied, learning to shoot with your dad, even being born.
Bright lights signify every important moment. As you're born, you see the white light of the medical equipment and your vision is blurred by your own birth matter. At your tenth birthday party, the surprise of the lights being suddenly turned on blinds you momentarily. When Amata wakes you up to tell you of your father's escape, sleep clouds your eyes as light fights its way in. This all culminates in the final transformation of your character, from Vault dweller to Lone Wanderer. As you step out of the Vault and into the world, the sunlight burns and blinds you. Your eyes eventually adjust, and the grimey greens and browns of the oppressively bleak wasteland contrast with the sterile blue and white sheen of the Vault.
This whole setup ensures you feel just as alienated as your character once you step out into the Capital Wasteland - instead of just projecting onto them, they project back onto you. It's a great way to narratively connect you with the character you're going to be roleplaying. That's the tone the other games just don't quite capture. That feeling of really being in the shoes of who you're playing as.
The tone outside of the Vault is also handled brilliantly. The Fallout series satirizes 1950s America and the politics and society of the time. This means that there's a lot of humor and wit to be found scattered among the nuclear debris. I think Fallout 3 strikes the perfect balance of funny and somber, while the other games fall too much into being overly serious or too comical. It's a hard line to walk, that's for sure, which is what makes Fallout 3 all the more impressive. While there are funny moments, like the Naughty Nightwear unmarked quest, these are balanced by the sight of burned-out homes, skeletons entwined in bed, the remnants of people holding each other for a few precious moments before they're consumed by nuclear fire. The absurdity and wonder of Harold - the sentient tree in Oasis - is offset by his pleas to end his miserable life. For every moment of happiness, there's one of despair, and that's important in a game about life after nuclear war. Fallout 3 isn't as hopeless as the earlier games, but it also isn't as much of a fun romp through the rubble as the later games are.
The world of the Capital Wasteland is what really binds everything together and cements Fallout 3 as my favorite in the franchise. It feels desolate and empty, but not in a way that bores me. The flat landscape means I can often see things on the horizon, but the walk there will be one of solitude, punctuated only by an attack by some horrifically mutated monstrosity. By comparison, Fallout 4 feels overcrowded. You're always near something or someone, there's no peace to be found in the Commonwealth. There's serenity in the emptiness of the Capital Wasteland. Rather than just bouncing from firefight to firefight, the empty journeys you take allow you to really reflect on the interactions you have and the impact you have on the world.
Of course, Fallout 3 is not a perfect game. There are elements in the other games that are way better. If you set your intelligence to one in the original games your character can barely read, making the entire game different. In New Vegas you have a huge impact on the outcome of the area - it also hugely improves upon the janky gunplay in Fallout 3. Fallout 4 and 76 have far better graphics, but I still think the visual style of Fallout 3 works amazingly. The NPCs aren't great, I'll admit that. They were scary then and they're scary now, with their unblinking gaze fixed onto your soul... But, the overall grit and filth of the world are perfectly applied. Even Tenpenny Tower can't avoid the dust of the Wasteland, no matter how high it builds its walls. The game isn't beautiful in a traditional sense, but the look of the game conveys a sense that everyone and everything is dirty no matter how hard they're scrubbed. It adds futility to the game while still rewarding and acknowledging the effort required to try and make life better.
All of the Fallout games offer different experiences, and if you think Fallout 3 is an ugly mass of greenish crap with awful shooting, then that's fine. But, for me, the coherence of the game's tone really sets it apart from the other entries in the series and makes it the best on offer.