I feel compelled to write this quick review having spent over 3 hours playing Fallout 3 since picking it up yesterday. I am taking the game back today, and this is why...
There are comments here about "if you are a hardcore gamer etc...". IMHO this is slightly off. This game will have you running around for many hours building up your character and exploring the world it has created, with no doubt limitless scenarios and quests to keep you busy. GTA IV, while a very different game in many ways this also has you following a similar path, albeit with a more linear narrative if you choose to work through the "story". What I really struggle with Fallout 3 is not the open ended and intricate structure, its the fact that the game is just plain boring. The characterisation is poor, the acting poor, the early part of the story feels stilted and while this may improve with 10+ hours of play, I simply don't care any more. Sure, the graphics aren't great, the combat system, which has some nice touches and I am sure will also improve as you improve your skills and get better weapons, just feels very unnatural compared to the level of immersion achieved in other games. The open ended story line has sacrificed good'ol game play, which just isn't necessary. A strong and believable combat system (like being able to understand what is going on with your weapons and how to quickly change them, even before you try to actually use them) and believable interaction with the characters would keep me playing, but in the event I am left empty, caring little for the characters or my situation. The attempt at humour, the stand off with early characters and even the potential love interest simply isn't believable or engaging in any way.
In summary, I am stunned by the array of top reviews for this game and can only put it down to a love of the Fallout franchise and Oblivion fans. I am a gamer, going back to the earliest computers and consoles, and while I have never really immersed myself in games like this on a PC or console, I really wanted to like this game. Ironically, with a complete overhaul of the script, characters and acting, more believable movement (all the characters walk and talk like robots, which simply isn't necessary in the advent of motion and performance capture) and an improved combat system would enable the deep story engine to draw you in. And the graphics are sub-par in today's next-gen world, but this could be forgiven with the above improvements.
So as I say, this is a warning, this may not be for you. Which really is shame.