Yes, the GTX280 is a better card for high res gaming than the GX2, mainly due to the larger frame buffer, no doubt. But it's sad to read that in some games, the average frame rate is lower than on the GX2 due to the bandwidth of the card
This card has 3x times the shading power of the G80, but only a 45% higher bandwidth. Remember what happened with the 7800GTX vs the 6800Ultra. 2x times faster in some games (2 MADD vs 1 MADD), but slightly faster on the rest (same bandwidth +-). Also, remember the huge boost that we saw on the 7800GTX512 when nvidia finally raised the memory clocks.
I think that nVidia should have put GDDR5 to allow the GT200 core to perform always 2-3x times faster, in ALL the games, and not only in those that are bounded by the shading power (Crysis).