Quite, simply, if those provided specs in thew OP are correct those are the numbers you would expect, .
Are they though? Looking at single and double point and memory performance compared to G200 cards, they look very high. They show the GTX360 to be 88% faster than a GTX285 in Stalker yet here is the comparison:
GTX 285 vx GTX360
Performance: SP 1.063GFLOPS VS 1.152 GFLOPS = 8% GAIN
Pixel fillrate: 20.736 vs 26 = 25% GAIN
Texel Fillrate: 51.84 vs 62.4 = 20% GAIN
Memory Bandwidth: 159 vs 168 = 9% GAIN
I fail to see how that can equate to an 88% performance gain in actual games. The GTX 360 is certainly faster than a GTX285 but maybe 20%.
In fact if you compare the GTX360 specs of bandwidth, fillrates etc, they are all slower than a GTX 295 yet somehow in those charts it manages to beat a GTX 295.
SO my best guess unless there is some magic going on, is that the GTX360 is going to be head to head with a 5850 and the gtx380 slightly faster than a 5870. I still reckon a HD5970 will still be the fastest card you can buy albeit dual core.
So it will all be down to price really. If Nvidia can launch the GTX360 for £200 and the GTX380 for £300 then it will be good times for consumers. Somehow, I suspect they will be more money though.