And that's why Fallout 3 is beeing made as a first/third person game (with 90% certainty anyway).
Like it or not but those newcomers, who don't know about fallout, will still end up making up a large percentage of the people that fund the current development of the game.
The majority of regular people that play, but aren't really "gamers", are usually between 10 and 20 years old. These are your average Halo guys, your WOW-guys, your PS3 guys etc. They play what's cool at the moment, or whatever their parents bought them for christmas. And few of them will know about a 10 year old isometric pc game, for them it could just as well have been pong.
So a lot of momentum has been lost in these ten years, the hype has to be built again. And fewer of these newcomers would want the game if it was beeing made as a top down game, which would mean less money in the bethesda treasury. And bethesda, at the end of the day, is a company like any other - it's all about the money.
Which is only a natural since, as games become more and more complex, the companies that make them are forced to become more and more structured and organized. Or - if you're a big nerdy gamer, I believe the term is "more mainstream". Like it or not but that's the way it is.
And I don't even have to stand for that conclusion myself because this is what the marketing guys at bethesda have already figured out, their actions speak for themselves. But it's not bad really, with a bigger buyer base comes a bigger budget, a bigger fanbase, and a bigger modding community etc - all good things.
So - in the long run, even though there occasionally may be places along the development of the industry where certain aspects of the games become lacking, it fuels the general development of the industry and gaming as a medium.
Just think that in the beginning of the gaming industy the thing that was lacking was graphics, but that now - with huge current leaps in graphics and audio - it may be the story, and character development, that is generally lacking.
But the tides will turn again... be in no doubt about it. It's all natural evolution... Darwin would be proud.