An amazing open-world RPG full of atmosphere.
It's a bit unfortunate that the main quest is a bit disappointing when compared to the rest of the game. Even more disappointing is the fact that you can't keep playing after you finish the main quest (at least without "Broken Steel", a paid expansion by the way), which sort of diminishes the replay-ability.
Visually, Fallout 3 is a stunner, breath-taking vista's and detailed indoor locations will make your jaw drop. The character models still suffer from the weird lifelesness that plagued Oblivion, but strongly improved voice-acting (with more variety in the voices) more than makes up for it. You'll still run across the odd visual glitch, but in a game this scale, it'd be nitpicking.
Overall, Fallout 3 is a great game and a must-have for any RPG fan.