How is it fair to compare PS3/360 sales to PS2/Xbox sales over the course of the entire generation? You can't ignore the fact that the PS2 was the console of choice for younger children and very casual gamers, many of which went to the Wii which you are discounting (and tablets/smartphones) this generation.
Opiate pretty much already covered me on this, but my point wasn't to try to separate core/casual or whatever. I used the term 'core' (a term which I hate) because that seems to be GAF's word of choice for distinguishing Nintendo from the HD Twins.
You are absolutely correct that PS2 had a segment which was a casual audience, and now 360 has built a segment there as well with all the Kinects sold the past couple holidays. The demographics are irrelevant to the point. The point was to compare the userbases which the publishers are targeting.
The publishers which GAF cares about (generalization) are EA, UbiSoft, Activision, THQ, Take 2, RockStar Games, Namco, Capcom, Konami, Square Enix, Sega, etc. And for the past two generations, these publishers have targeted PS2/XBox and PS3/360. For whatever reasons you want to go with, they ignored Gamecube and Wii. Their only efforts on Cube/Wii were lazy ports, spin-offs, party games, mini-games, dance/exercise, or lower-tier devs working on a new IP with a small budget. (The only real exceptions were Resident Evil 4 on Cube, and Epic Mickey on Wii - and Monster Hunter Tri, but that was pretty irrelevant for NPD discussion). All of their top studios, top mainline brands, top dev budgets, top marketing budgets - it all went to PS2/XBox and PS3/360.
That's why I illustrated that comparison, because in that context, for those publishers on home consoles, it has taken longer to get to the same userbase than it did last gen, but costs have risen significantly. Which again makes it pretty easy to see why so many studios have been closing down and why so many publishers have been bleeding money this gen. (The Japanese pubs were sheltered somewhat from the big losses because they were smart enough to branch off into major handheld development as well - something which the western pubs have just recently started dipping their toes into with mobile, but they are still a long, long way from actually committing some of their top dev teams and budgets to the mobile space).
Edit - And having the generation drag on longer can be a very good thing for MS/Sony/Nintendo. Generally speaking, late in the gen, the hardware is sold for a profit, the R&D costs have all been recouped, and 1st-party software and 3rd-party licensing is pretty much free money. But for the publishers, a gen that drags on isn't really as good as it may appear. The longer the gen drags on, the more churn there is in the userbase. People that got in early in the gen, and have gotten bored with playing the same version of the same games for the 3rd/4th/5th time, and they've just chucked the console on a shelf somewhere and moved on to other games - PC, 3DS, iOS, Facebook, whatever. The longer the gen drags on, the more churn you get every year, so the actual active userbase isn't anywhere near what the late gen numbers suggest, and the newer customers that come in every year are typically budget consumers. And those budget consumers now have a whole back-catalog of excellent games available at $15 or $20, and those are the games they end up buying. Not the shiny new $60 games the publishers are trying to sell.
Because it took longer for PS3/360 to get to the same point as PS2/XBox, the average userbase growth per year has been smaller this gen than last, and with the longer generation, the churn will also be a lot higher this gen.
So the publishers are looking at trying to drag this gen out even longer (even though this has been a horrible gen for most of them - and many of the newcomers to the gen now will be much more budget-conscious consumers), or try to spur on the advance of the next gen (where they are looking at pretty much the same userbase they've been selling to the past two gens, but with a real chance at significantly higher costs once more). Really, they need to either find a way to seriously cut costs, or they need to find a way to expand their market beyond the PS2/XBox - PS3/360 base).
