The Original Fallout games - but not in the image of Fallout 3. As much as I like Fallout 3, I wouldn't like to see a remade Fallout 1 in that style. But give it a graphical upgrade, more dialogue and additional areas and endings, do the same for Fallout 2, and you'd make me a happy gamer.
Of course, it wouldn't really make that much of a profit, which is why Bethesda won't do it. Sure, die hard fans of Fallout would buy it, but I don't think many new users would. So the odds of a fallout 1 and 2 remake are not good, to say the least.