What? FO3 was basicly FO1+2+ tactics stories shoehorned together. With weak explanations that didn't really mesh with established canon thrown up to try and hide the gaping holes.
It is indeed, to an extent, a throwback to the main plot lines of previous games...most notably Fallout 2's main arc of dealing with the Enclave. However I find that aspect of the story in Fallout 3 to be more of an extension rather than a cheap copy/paste. The other aspect of the main storyline which involves the search for the PC's father and project purity was, while certainly not as deep as I would have hoped for, enough to stand on its own from Vault Dweller's single man war against the Master or Chosen One's plight to save his village.
I played through the core FO3 game (I don't have any DLC's) I can safeely tell you that you have about 2 "real" choices for any given quest. That effect the ending. So in reality by your second playthrough you've seen and done everything there is to see. You certainly will see the same ending cutscenes over and over again.
This is true that in the original games (F-F2) there were more variations in the endings, particularly because they expanded more on each township's outcome as opposed to F3's more general overview ending. However while the voiced epilogues may be different, you only ever see one of 2 snapshots anyway so visually there is only 2 outcomes per city.
Nonetheless, I very much wish that F3 would have had more variety with choice and consequence as the previous ones did, or at least I would have been happy to have also have the game focus an ending on each one of the major locations of the game: Megaton, Rivet City, Paradise Falls, Big Town, Oasis, Little Lamplight, Underworld, Tenpenny Tower, Raven Rock, Canterbury Commons (Which should have been much bigger like the Hub of the original game to begin with imo).
Wow not changed? Not only does it not use the previous installments mechanics it doesn't have the same gameplay, art, or lore as the others. While yes, it does use the previous lore, it also adds things in that "streches it's truth" so to speak. For example, SM in D.C. If you go by the lore in previous game you know that FEV was in one place and was destroyed. However in FO3 now we are to al of a sudden believe that Vault tec, not west-tec where doing experiments too with FEV? See what I mean? they sorta first added in the enemies then thought up weak reasons that could barely hold up to lore to "excuse" there existance.
Gameplay is radically different as has been discussed ad nauseum but I actually like this change.
Outside of other lore infringements I am not familiar with at the moment, the Capital Wasteland FEV experiments are explained in content which was cut from the final game (Sadly) which involves a researcher who was sent to Maripossa. Ausir found this log entry.
Oh, I'd say it was greatly tempered from previous games. Not only does it not have the same elements of six, drugs, desperation, and despare you see in the previous games, it's missing componets all together. IT also try too hard in some other cases. and is too generic in other places. Most definately in the C&C areas and dialogue. Quests are pretty black and white too.
Also agreed, but I also have to argue that for the most part quests in the original games were black and white as well, save for 1 or 2 exceptions.
As far as F3 goes, the most morally ambiguous quest imo relates to the one in the Pitt and to this moment (While the game does divide between good karma and bad karma for it) I haven't a clue which is really the better decision.