Being the minimum for what it takes to run and being what it takes to run good is two different things, if going by your premise then the XP box should have had 512mb of ram instead of the 1 gig, which would have been twice what XP’s minimum requirements were.
Part of the problem is that the industry as a whole, and this really is not just a MS crime, lie like rugs about system requirements. In an effort to get more people to buy their product they put forth numbers that are just a fiction, sure most apps/ OSes will start on a system they speced but that’s about it. XPs recommended is 128MB, which is laughable, anybody that tries to run XP with less than a gig is being silly. Vista’s recommendation is 512MB, again laughable, some folks say 2GB is fine for Vista, my usage says don’t even think about it until you hit 4. 4X to 8X seems to be MS’s fudge factor, take what they say multiply it by somewhere between 4 and 8 and you’ll actually find out what the product needs.
Again this isn’t just an MS thing, the recommendation on EA games is silly, their fudge is 2 to 4. Even the app I work on, what we say is about half the system I’d be willing to even try to work the app on. Somebody should start a website tracking the difference between their recommended and user recommendation, kind of like the sites that track MPG stats.