Jaime Lannister said:
In terms of setting, 1>3>2.
In terms of role-playing, 2>1>3.
Well, in terms of setting, there honestly shouldn't be any Supermutants, BoS, or Centaurs in Fallout 3. If there are Supermutants on the East Coast, they should be really, REALLY rare. Only so many Supermutants were made at Mariposa on the West Coast. How many of them would die along the way?
The BoS only has so many resources and they're based in Lost Hills. Even if they followed the plot of Fallout Tactics, the BoS would have only expanded so far in the amount of time between Fallout Tactics and Fallout 3. The end slides of Falliut Tactics kind of implied they were expanding West as well. If the BoS expanded quickly East, they would have trouble gathering resources. Things would break down and need to get replenished, so you'd have to stop and gather things. The BoS has lots of technology, so they rely on it heavily. If they double time marched fast towards the East, and things were breaking down on them, they'd be screwed. Sure, the BoS have great amounts of pre-war tech which is a plus when it works, but when it stops working.. The BoS wouldn't survive nearly as long as typical wastelanders. They've never had to survive on their own without their technology.
The Enclave is kind of silly as well. The Enclave moved West before the war. If the Congress survived the war, they probably wouldn't have called themselves "The Enclave", since the The Enclave was basically the executive branch that abandoned them to be killed by the bombs. It'd be like the Cinncinnati Bengals renaming themselves Cinncinnati Steelers.
I just kind of wish Bethesda had gone their own creative route with Fallout 3 as opposed to taking everything that existed on the West Coast and put them on the East Coast. There's a lot of room for creativity there, I just wish they'd attempted to use their brains to come up with something new as opposed to making excuses for why the East Coast looks like the West Coast with monuments.