If you ever played Fallout 1 and/or 2 (or New Vegas) you'd probably associate Fallout games with things like: The writing with its deep, elaborate lore and detailed world building as well as dark, sarcastic humor and interesting ethical dilemmas. With fun '50s sci-fi pop-culture references incorporated into the setting/world, not just sprinkled on top. Choices, that are often complex and (tangents on) philosophical, branching paths and endings that are influenced by actions and statements made throughout the game. A world that feels alive (in a post-apolyptic sense). I experience none or very little of the aforementioned things as I played through Fallout 3.
This is the spiritual sequel to Fallout New Vegas (and Fallout 1+2), and in part because it's not limited by Bethesda's Fallout 3 engine (and it's assortment of bugs) it is superior to New Vegas. A game which was superior to Fallout 3, 4 and '76. The writing is witty and engaging. The environments are lush, garish in a good way. The world building draws you in, feels like it was built with a great foundation and fleshed out. Enemy designs range from pretty nice to fantabulous. Quests are quite varied, their narratives are interesting with a lot of 'gray ethics' (not black & white what's the just solution), many have quite a few ways to complete them and it impacts the experiences going forward. On a techical note, I've not experienced a single bug. I'm sure it has bugs (which game doesn't?) but not in any way near the sheer quantity of bugs in Fallout 3, New Vegas, 4 & '76. (Own it on a separate platform with DLCs)
