Great story, great atmosphere, bad acting.
The entire game is played out as a story. Even in the tutorial, while you learn all the controls, the story is important. One very early conversation, shortly after you learn how to pick up and carry objects, seems trivial but then becomes a major part of the story later. The story sucks you in, making you feel as though you actually are the person you play. Unfortunately, most of the voice acting is very badly done, with characters who are calling you names sounding more like they are happy than angry. "Dad" is one of the few characters who has a good actor.
One of the fun things in the game is creating your character, yet it almost never is seen after that. V.A.T.S. mode is one of the few times you can see your character from many angles, but even then helmets and such will block your view. Even when bareheaded, your character's expression never changes, making him seem plastic. The name you create serves no other purpose than to mark your save files, as none of the NPCs use it. The karma system is interesting, but has little real purpose other than deciding which followers you can have. Good players will occasionally recieve free gifts from NPCs, while evil players will be chased by regulators, but other than that it has little effect on gameplay.
Combat is very fun, as hits on certain body parts actually effect the enemy. Shoot his le enough and he will be reduced to a slow hobble. Shoot his arm and he will have trouble using his weapon. Shoot his head and he will be much less accurate, often shooting at his friends. V.A.T.S. mode helps your battle by freezing time, zooming to the enemy, and allowing you to target specific body parts. Death sequences can be hilarious, will a swipe from a Deathclaw Gauntlet sending someone flying over a fence, or a shot from a rifle exploding his or her head.
Skills are the most immportant part of the game. If you choose the wrong skills early on, it can cripple the rest of your game. (This can be remedied by reloading at the Vault entrance, where you can completely remake your character without having to redo the entire tutorial.) Every skill is important, but you will have to make critical decisions, as you only have a limited number of skill points per level up to spend on your skills.
Weapons in Fallout 3 are, for the most part, very solid. An assault rifle is inaccurate, but makes up for it by having a fast rate of fire. Shotguns are devastating at close range, Sledgehammers can crush an enemy's head. The relative scarcity of ammo means that you will have to choose which weapon to use depending on the amount of ammo or its condition. As they are used, weapons degrade and eventually break. They can be repaired by finding a second gun of the same kind and combining them, or by paying a shopkeeper to repair them. Guns with higher condition do higher damage.
Fallout 3 combines FPS and RPG to make a great game that can provide hours of gameplay. With the 5 DLCs available, you can become a walking weapon of mass destruction, effortlessly taking out even the largest of foes. I will probably be playing this amazing game for the next few years. I highly recommend it to anyone who wants a FPS with a great story.