This thread is quite old so the whole discussion part is moot. W8 will be out in a few months and you can start the discussion again.
There are definitely some games that run better or even "need" settings of Vista or XP to work properly.
As for memory and CPU processing power, newer games of course tend to need/use more because they are designed to use the power of newer machines and hand-in-hand games needing more is one of the major driving forces for PC manufacturers to make more powerful machines.
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