That's a new chapter of our civilization.
At the begining in the 80's, with Oric, Commodores, Amstrad CPC etc... there was very difficult games with no synopsis not attended to be finished, just pure gameplay.
Later, there was games that you can even finish by being a true r0xx0r. Later, in the 90's, there was games with more or less synopsis, a begining and an end and true gameplay. some were called CRPG and fallout were part of it.
At the end of this period, the videogames begun to be a worthy indistry making money and begining to have his place next to music and cinema.
Then there was a new dawn. The dawn of the big industries that needed to touch a whole market... the scenario and the graphics beguns to encroch the gameplay and the depth of the gameplay.
Today, the industries - who want more and more money, because we have never enough of it, isn't it ? - can't sell a game if 12 years old childs cannot play it. Too much lack of earn (don't know if it have a sens in English, but you get the point).
Now, if you really want a fallout 3 that is the perfect sequel of the initial serie, you need to :
1 - wait for a opensource project to make one
2 - find a rich person who don't care loosing millions of dollars by hiring a crew of developper and give it in free download on the internet or selling it illicitly (because ESRB will never allow anymore a game like the originals fallout with the abilitie to kill children, being an hooker or a porn star to be selled in any marketplace)
Sorry for my lacks in english, hope that you could decipher it ^^
And, to finish :
This isn't "the chicken and the egg", we know what came first.
Actually, the first was a single cell organism
