As somebody who, admittedly, read the complaints of the Fallout community for months about Bethesda's involvement in Fallout 3 instead of original developer Interplay, I had some concerns. True, I like the Morrowind series and thought Oblivion was inspired, but the fans were OUTRAGED~! about the travesty that this game, surely, would devolve into.
The game, honestly, is amazing. One of the best RPG's in the last 2 years. Not without some flaws, but nothing to make the game less than a probable RPG of the year. The return to post-nuclear apocalypse America (Washington, DC to be specific) is a deep experience.
You start off in Vault 101 as you're being born and mature into an adult in a brilliant character customization system. You are given free reign to set yourself for the rest of the game.
The usual Bethesda RPG system of receiving side quests while doing larger quests is still in full effect and fits Fallout magnificently. Many Fallout enemies return as well, giving you a nice tie-in to the universe. You get a few unique ones, but the old radscorpions you fought incessantly in the first two games are here. In force.
Visually, this might be the best looking RPG ever made. The facial models are still fairly "meh" as tends to be the case with the Bethesda engine, but everything looks beautifully...well, destroyed. The cities all look like pockets of survival in a world destroyed by a nuclear holocaust. Every building, for the most part, looks like it was built out of debris from something else. Nothing looks clean and orderly. Everything looks suitably ravaged by destruction. The enemies also look really nice. The mutants look menacing, the undead look...decomposed, and the animals look similar to regular animals, but with enough differences to make you realize that life has gone poorly for the last century or so.
The soundtrack is a nice collection of music that, if not actually vintage 50's music, sounds very much like 50's music. There is a ton of voice work that is all decent --- an improvement over the usual terrible voice-over work in gaming.
The biggest strength, though, is the freedom you have. You can free slaves --- or capture them. You can disarm bombs --- or wipe out cities. You can be good or evil and the game is eminently playable either way. You can steal stuff, but the town will hate you. If the town loves you, they might give you gifts. You can improve your weapons by using other versions of the same weapon to improve yours. The game is one of the rare ones where you can win no matter what path you take.
Not to say there aren't problems. Downtown Washington DC is linear --- certain areas are only able to be reached by specific locations. There are walls of debris all over the place. I'm sure it's a design consideration, but I hate "walls" such as that in an open world game. The framerate will plummet here and there. Animals are surprisingly focused --- they will follow you for LONG times to attack you. And you are able to make it so you cannot do specific quests (quest-givers should not be killable until you have done their quests). Level maps are nearly useless as most of your "dungeons" (for wont of a better term) are multiple floors and they tend to overlap a lot.
But these are nit picking and little more. The 35 hours it took for me to beat this (and that was much time killed for one irritating mission and grabbing achievements) flew by. It wasn't overly difficult (you are really tough) but it was a fun play regardless. I can't recommend it highly enough. It's even better than Oblivion, which was my favorite RPG ever.