Issues with combat derail some of the fun, but taken as a whole Fallout 3 is unbeatable in terms of atmosphere and value
Fallout 3 begins with your birth, literally. You begin the game as an infant exiting your mother's womb into your father's arms, and it is at this point you determine your gender and appearance. However, soon after your birth, your mother passes away, and soon after your life begins in Vault 101. Vault 101 is a sanctuary from the wastes, the descendants of those who hid underground when the bombs fell, so it is a clean, safe place, but a rather dry and sterile one. So while much of what amounts to the game's tutorial takes place here, it would be terribly boring were the main game to take place here so naturally, the inevitable conflict takes place that forces you to leave. Your father decides to leave the vault and return to the outside world in which he was born, in hopes that you would be safe inside the vault. The overseer of the vault, who is a bit tyrannical in his own way, does not like this, and all hell breaks loose. He sends his men after you, so escape becomes a necessity. With help from his daughter, you do escape the vault, and enter the wastes in search of your father.
After leaving the vault, you are on your own. Your quest arrow points you to Megaton, a city build around an undetonated atomic bomb, and it is there that your search begins. Your search for your father will take you all across the wastes and put you into the acquaintance with many memorable characters and places. Outside of the great main storyline, there are plenty of side quests to go around, but with the lack of major cities and the difficulty of navigating much of the wastes, they are often hard to find and sometimes feel too few and far between. Most of the quests have multiple endings (including the main storyline, which involves your father's life work to help save humanity), which let you determine how things turn out in the wastes. Also, most of the major side quests have achievements tied to them, which is a nice bonus to receive after each mission.
Fallout 3 features a good/evil system which is central to these decisions you make in both the main quest and the side quests which are offered. For making good choices in the world you are awarded karma, and the higher your karma the more noble a person you are. Conversely, losing karma makes you an evil character. Whatever your karma may be has little direct impact on the game outside of what achievements are gained for reaching a certain level, it is the choices you make that leave an impact. For instance, one quest centers on the bomb in the center of Megaton. You can either help out a mysterious man who offers a great reward for the city's demise by detonating the bomb, or out of the goodness of your heart, help out the residents of the town for a much smaller reward. Thus, an entire city's fate rests on your actions, and while that is probably the most dramatic consequence the game offers as a result of a side quest, other quests do have some sort of an impact. A radio broadcaster will often praise or lambast you depending on your actions in a radio show broadcast across the wasteland, which is fun to listen to and makes you feel like you are leaving your mark on the world.
The game's skill system is mostly based upon that of the old Fallout games, the SPECIAL system being the foundation upon which your character is built. At the start of the game, you are given an amount of points to distribute into your main attributes of Strength, Perception, Endurance, Charisma, Intelligence, Agility, and Luck, each one determining a certain aspect of your character. For example, with a high strength level, you can carry more items (in terms of weight). With a higher Perception, enemies appear on your radar from a farther distance than they would normally. How many points you have in a certain attribute determines what perks you can take. Perks, which you can take once per level up, can have a major impact on your character. They can do fun things like cause bodies to explode after death, to increasing your skills, to causing fingers to spawn on evil character's dead bodies, which can be turned into a group of good characters for money and experience. With the right combination of perks, you can become a powerhouse of a character, but choose carefully, as some are totally useless in the long run.
Skills have the most direct impact on the game. For example, lockpicking makes picking locks easier, or grants you the ability to pick harder locks. Science lets you have into terminals more easily. Medicine makes healing items more effective. It is all rather standard fare, but you want to make sure you maximize your skill point gain upon leveling, as each skill has its own use which comes in handy.
Combat in the game is an interesting combination of fun and frustrating clunkiness. The gun and swordplay itself is rather poor. Since the game plays and controls nearly identically to Oblivion or Morrowind because the game was produced by Bethesda and uses the same engine, shooting doesn't quite work right (though the guns all feel appropriately powerful and the selection of guns and armor leaves little to be desired, so this is a non-issue). It is very hard to aim, and overall things just don't quite feel right. It is hard to put into words why, but the way the game controls doesn't feel right. You turn so slowly, even on the highest sensitivity settings, than being teamed up on can lead to a quick death because you simply cannot do what you want to do fast enough. Combat is redeemed by the VATS system. VATS lets you slow combat down to a stop, and target specific body parts on your enemies and then attack, to a noticeable effect. Crippling an enemy's leg will cause them to limp, or crippling their arm will cause them to lose accuracy. The action all takes place in slow motion, with all the gore and bloody goodness that comes with it (the animations here are absolutely top-notch). However, VATS use is limited by your weapon, your agility skill, and your perks, which determine how many action points you have and how fast they are used up. Once your action points are gone, they slowly recharge, and while you wait for what amounts to superhero mode to become usable again, you are thrust back into the awkward combat which makes things more difficult than they should be.
Perhaps for some of the wrong reasons, Fallout 3 turns out to be a rather difficult game. Not unreasonably difficult by any means, but harder than the average game these days, especially early on when your skills are low, ammo supplies limited, and guns near-broken. Yes, in the wasteland, ammo is very scarce, and you as the player can only fix your weapons from other weapons of the same type (the same going for armor), as are healing items, which you will need, as combat comes hard and quick at you. Of course, vendors are willing to repair your goods or sell you ammo for a cost, but early in the game the opportunity to earn caps (bottle caps are used as currency in the wastes) simply aren't there. Everything and seemingly everyone out in the wasteland is out to kill you it seems at times, and you'd better be prepared, or else death will come swiftly.
The challenging atmosphere, however, makes the game better. You really do feel like you are barely scraping by at times, which is exactly what you'd expect out in a nuclear wasteland inhabited by super strong Super Mutants or dangerously mutated animals. You always feel on edge while playing, like at any time you could step on a leftover mine from the old war and have your leg crippled, walk into a pocket of radiation and gain radiation sickness (the game keeps track of how much radiation you have absorbed, too much radiation causing skill decreases or even death), or simply come across a large group of enemies and have to frantically fight for life. That, along with the game's impressive visuals, set in the instantly recognizable Washington DC ruins, makes the atmosphere of this game unbeatable.
The game's creators clearly set out with the goal to make the game as depressing as possible in terms of appearance. Most of the land is simply nothingness, barren land with perhaps the occasional building, highway overpass, or shrub. The Super Mutant infested ruins of the city of Washington DC are the closest you'll ever get to the old world. Underground, the subway tunnels are largely intact, and you'll spend a decent amount of time inside of them as some areas can only be accessed via the tunnels, as rubble of ruined buildings blocks access to some areas. The only criticism of the appearance I can think of is that the buildings seem too intact for being through a nuclear impact (or two), and for being neglected for 200+ years. But I suppose if they went the fully realistic route and left virtually nothing out on the surface, there's be no game to play. The game's sound effects are all up to par with the visuals and the music appropriately atmospheric, which adds to the outstanding atmosphere the game presents.
While most people you encounter are hostile towards you, there is still plenty of interaction to be had with the people of the Washington DC wasteland. While communication is exactly identical to Oblivion minus the spacecraft game, the people's facial expressions are improved and the voice acting superior to the older Oblivion. If you have never played Oblivion before, dialogue results in a list of topics coming up, and asking about a topic leads the NPC talking about the topic. Conversation is awkward in that the person you are talking to stares you unblinkingly right in the eyes, with a look some call the "Bethesda face," an emotionless, almost creepy look which is just weird and artificial. There is some room for improvement here in terms of NPC interaction as most of it is just listening to what they have to say and occasionally giving what amounts to a simple "yes" or "no" to what they have to say, but interaction works well enough to keep the game moving.
Fallout 3 has five add-ons, most of which are nice to have, but largely inessential. The only add-on I would call essential is the Broken Steel add-on, as it raises the level cap, extends (a bit absurdly) the main storyline, and adds new places in enemies, all of which add to the experience of Fallout 3. Mothership Zeta revolves around your character being abducted by aliens and your ensuing escape, and while a fun distraction, it is simple, poor in terms of story (and logic, how could super advanced aliens allow one man to take over the ship?), immersion breaking, and largely inessential. Operation Anchorage places you in a simulation of the United States' recapture of Anchorage, Alaska from the Chinese, and is surprisingly fun. However, it too is largely inessential and focuses on the game's weak combat system, though the game-breakingly strong rewards the add-on rewards are a fun to play around with afterwards. Point Lookout is a decent add-on in terms of content, as instead of one short quest, it offers a whole new area to explore. It is a decent addition to the game in terms of area to explore, new items, and missions, so I would recommend it if you have the money for it. I have not yet played through the "The Pitt" add-on and my update this review after I do, but for now, I will say I have heard good things about it.
In summary, Fallout 3 is an excellent game. It has one of the most memorable and addictive atmospheres of any game I have ever played, and the fact that you can shape with world and its fate through your actions is great fun to experience. The combat outside of VATS is poor, and the conversation system a bit awkward, but these flaws are minor in comparison with all the positives the game offers. The add-ons are mixed bag, but the Game of the Year edition is worth buying, as it has all the add-ons included along with the main game (a good 40 hours of content), a great deal for $60 (and for $20-$30, the main game alone is also a great value). The ruins of Washington DC are certainly worth visiting if you have the time and if you haven't already, so if you have any love for atmospheric games or RPG's, give Fallout 3 a shot, you will not regret it.