I have yet to find a more accurate source.
There may be more accurate sources for individual territories, but nobody compiles more info from around the world in one place. If you want more than 3 or 4 numbers, VGcharts is easily, far and beyond, the best source.
"[Our former customers] are unable to find software which they WANT to play."
"The way to solve this problem lies in how to communicate what kind of games [they CAN play]."
Satoru Iwata, Nintendo President. Only slightly paraphrased.
I'd argue that VGcharts has lots of quantity, but not as much quality (not in a bad way). IE, the whole US/NA methodology: Take a number, round it to the nearest 1/4 thousand, then multiply by 10%. As much as that supposedly should work for Canada/Mexico, the market(s) are more like 6-7.5% of the US's NPD total as opposed to the 10% VGcharts.org extrapolates. Japan isn't as bad, as they use Famitsu which is already rounded. Of course, I prefer MC for data is it's not rounded. Of course, it's kind of a chevy-ford thing with famitsu and MC. Worldwide, it's anyones guess. However, the numbers are pretty close as they emulate official numbers from MS/Sony/Nintendo's ship numbers with a decent bit of info on actual sellthrough. That obviously can't be very accurate due to smaller territories like European, Austrailian and other asian territories.
Back from the dead, I'm afraid.