Thank you so much for making this thread kowenicki. I had the exact same frustrations as you where in that news post there were so many people who had simply looked at the graph and gone ''Oh well Vita is actually doing amazing'' and were ignoring the differences in launch times.
Of course as others pointed out at some point you will have to add notes about timing differences with large sale periods. However in the long run it will average out. Keep the thread updated! You can do it!
I think the most worrying thing so far is that despite launching MUCH bigger in Japan the Vita is already considerably behind the PSP after 3 months and it's weekly sales are also lower. Whereas in America and Europe the vita has even launched much lower than the PSP and we will have to see how following weeks go.
Does illustrate quite nicely just how much hype there was for the PSP with Sony coming off the highs of the PS1 and PS2, with people hoping it would be a portable PS2. In contrast the Vita is launching at a time when Sony are in a much weaker market position.