Immersing oneself in Fallout3 there is absolutely no feeling of being in anything other than a FALLOUT game.
Maybe for you but not for me.
Super mutants made no sense for me, Vault-Tec shouldn't have access to the Pan Immunity Virus/Forced Evolutionary Virus and super mutants should not be orcs that just rampage through the world with no goal other than to "kill puny huumanz."
Ghouls looks like burned victims, and they run, and they can wear power armor and all of the sudden they can go "feral" as well.
The worlds houses and buildings look nothing like the architecture of the previous games' buildings.
Radiation is now found everywhere.
People don't have any agriculture going on.
Electricity still works throughout the land with no power source to be found.
Factions were underdeveloped.
Towns were like populated by two to four dozen people and had no production going on either. (It's been 200 [censored] years!!)
Jet, a creation by sweet young Myron who died before his prime, magically appears a continent away.
Vault doors open inwards.
No weapons from the old games can be found.
BOS are white knights while Outcasts are petty last minute additions added as a minor reference to the original BOS.
Enclave which got blown to Narnia are all of the sudden back with crap weapons and power armor and try to do THE SAME BLOODY THING THEY DID LAST TIME! (Did they learn nothing!? Don't control [censored] deathclaws and don't try to use a virus to wipe out all life on earth!)
And much much muuuuuuch more.
If you could play the game and feel "this is Fallout", then good for you I guess, but I played it and I was like "What kind of half-assed attempt at Fallout is this?".
So no, I did not feel like I was in a Fallout game, I felt like I was in a post-apocalyptic game "loosely inspired" by Fallout.