Those system req are not very accurate in my opinion. The recommended GPU for tomb raider underworld for example is 9800GTX, but I was able to play the game on highest detail at 1680x1050 with 8800GTS 320MB !
However, the recommend specs for Crysis is 8800GTS 640MB, but I can't run this game smoothly if I play it on anything above medium details.
So, don't take those recommended specs seriously