Why are you looking at just one game, again?
How about this one:
Or maybe this one:
Two of the best looking games out there, and pretty easy to find benches of 5870 Crossfire running right with or outperforming 480 SLI.
Now I'm not posting these to say that 5870 Crossfire is stronger, but you need to look at more than one title to get an accurate picture of performance. There are several titles that 5870 Crossfire competes quite well in.