I'll agree that the 6000 series isn't all that much better than 5000 but it's not like nVidia's doing any better. I don't see how AMD's less powerful than nVidia, though
. I mean, sure, the green guys have their GTX 580 which holds the single GPU crown but AMD has 6990 now which, considering all the problems plaguing the 590 ( hot news - nVidia locked voltage tweaking with drivers to keep the cards from blowing up ), is the slightly better card.
All in all, nVidia is still hurting from the whole Fermi fiasco and AMD ended up with the wrong production process for their 69XX cards. I'm surprised the most at how pathetic Fermi turned out to be. First gen of these processors was hardly better than their GTX 2XX cards and the current gen reached it's limit while still falling a little short of AMD's design.
I'm waiting to see how both companies will do with smaller manufacturing process used in next generation of cards. Currently, both top cards are ridiculous with heat output and power consumption. I thought they were moving in the right direction when the 5970 was released.