10's have to be earned. And Fallout 3 earned it.
Still to this day, over a year after it was released, this game has graphics that easily beat modern day games. The way they manage to give you the feeling you are walking trough a post-apocalyptic post office, is just great.
The story also adds to this. The main quests are good. Not as many twists as I would like, especially in the add-ons, but they are a lot of fun to do, and have you exploring the entire D.C. Wasteland.
The real treasures are hidden in the side quests. They all, big or large, open up new dialogs with characters you thought you knew. Now this also adds some bad things to the game. All of the sudden you know who this holotape should be brought to and who is related to who.
Beyond this, the side quests have you exploring runes and landmarks like the White House and its high security metro station. It all adds to the overall feeling the game gives. A hopeless depressing world, waiting for a helping hand.