This is not generally true. I have the NPD for every month.
In the historic fashion it certainly is. The synchronized launch-to-date sales are within ~5% deviance
Compare the deviance against NA sales for syncrhonized launch-todate with the PS2. I have ~13.9M PS2 NA sales from launch-to-August, and ~6.12M NA sales for the Xbox 360 from launch-to-August. That is a staggering 100% + variance.
Even counting your "exceptions" as reasons to dismiss the value of certain sales periods (which is a never ending list), in the big picture I don't doesn't invalidate the trend.
And the trend being the Xbox 360 is trending in launch-to-date sales very closely to the Xbox and is falling significantly behind the historical trends of past market leaders.
Basically, versus Xbox, 360 was put at a huge disadvantage because it was supply constrained it's first holiday, whereas Xbox 1 was not. After the first two months for each console, Xbox 1 was ahead by 814,000 consoles.
I won't dismiss it is at a disadvange, but some points.
First is that in terms of historic trending or launch-to-date trending it doesn't really matter.
Second, even considering your data, MS isn't trending substantially better in NA. We are talking about a different of 20% instead of 5%.
People can note launch shortages, MS not price cutting, bad press from the RROD, higher pricing schemes, reduced production and sales in H1 2007, and the other various hurdles the 360 has faced. Yet those, too, have become a trend.
Which all obscured the point that I think is most important:
From a historic position the Xbox 360 is trending toward a 2nd/3rd place console in regards to market share.
I do believe holiday 2007 will be a big boom for MS (if they can meet supply). I also believe the Xbox 360 is going to substantially outsell the Xbox in lifetime sales--in my estimation MS will reach 2x increase in sales.
And to play devils advocate, you want to disregard the first 2 months of Xbox 360 sales because of supply constraints. But it could be argued that, after 19 months, that should have been equalized. If the sales trend was substantially stronger, all those spurned launch consumers should have bumped up sales significantly in the spring plus the increased sales rate. Did all those spurned launch consumers dissappear and never buy a console? It is easier to argue that they are a large part of the increased sales rates. So it isn't as cut and dry as diregarding those numbers. In the big picture that, after 19 months, we need to still excuse launch shortages as a reason NOT to compare launch-to-date trends says more than I ever could. MS obviously didn't capitolize in the way they should have. Which was my point about spring/summer 2007 sales -- you don't magically make those up in the fall. The price cut was too little, too late.
And lets not forget that every arguement you make for the Xbox 360 can be made in a similar fashion to the Xbox: It launched late, had less publisher support, didn't launch with Live, had 2 consoles to compete with at launch, had no known IPs, lacked a fanbase, etc.
If we compare and contrast the obstacles the Xbox and Xbox 360 had in the market, I would say the 360 has faced less competition and fewer obstacles. Should we factor this into our sales data?
Not if we are comparing launch-to-date sales trends. In those trends, as you note, the Xbox 360 is on an ascending trend -- but it isn't significant, to this point, in regards to historical market leadership rates.
That honor would befall the Nintendo Wii.
While your points are valid and point toward better-than-Xbox long term sales for the 360, in the historic perspective it is akin to Sony getting excited about a 100% increase in monthly sales, yet a.) lagging behind both competitors and b.) completely off pace historically.
At MS's current rate they won't be aquiring many of the 120M PS2 customers who are undecided on which next gen platform they should purchase. Right now it looks like the Wii is the one making the most inroads in that market.
That said, I do see things looking up for MS, as I mentioned before. Software is a driving force, and MS is excelling in that department now.
EDIT: Stealth edit Rangers FTW! I see that we both see what the other is saying and I agree. And longterm I do see the 360 doing better than the Xbox, by a substantial margin.