The GX2 is a single card, but it's not a single GPU solution.
So if you compare dual GPU from nvidia, to dual GPU from ATi, then that's the proper way of looking at it. You should not compare a GX2 to a board that just has 1 GPU. The only reason it's done in reviews is to show that ATi's single GPU can compare with nvidia's dual GPU in some instances/games.
So if you compare dual GPU from nvidia, to dual GPU from ATi, then that's the proper way of looking at it. You should not compare a GX2 to a board that just has 1 GPU. The only reason it's done in reviews is to show that ATi's single GPU can compare with nvidia's dual GPU in some instances/games.