8800 GT = 9800GT but with new chipset. 9800 GT = 9800 GTX but overclocked. 9800 GTX = 9800 GTX+ but with different chipset and overclocked more. 9800 GTX+ = GTS 250 but overclocked.
8600 GT = 9600 GT but with new chipset, which makes it faster than 8600 GT.
8500 GT = 9400 GT but with new chipset, which makes it faster than 8500 GT.
And so on.
My 9800 GT:

My E5200:

Everygame made so far, and I have not even single FPS problem with them, with any graphics. People over underrates 9800 GT, as it is "expensive" compared to HD 4850? What I've seen in my local shop, 9800 GT is cheaper than HD 4850. Mine PC runs Crysis with Extreme Quality and 1920x1080, 4x AA.
But, if your Ati fanboy, there's nothing that can change it
