I disagree. You should compare against the lifetime of the product, starting from initial release until the producer stop producing it. Not just by its first week. You will then get a true picture whether product A is more successful than product B.
My colleagues in logistics division used to tell me that comparing first week sales of different products within the same family is like comparing apples and oranges. They're just not comparable.
In supply chain, first week sales and preorders are mostly used to gauge inventory level and reorder plan for subsequent production batch. You don't book your order to manufacturer to produce one million copies at one go. You stagger based on the demand of the market. This is necessary to avoid goods return due to oversupply which can result to write-off.
The key value is actually the demand rate across period. There are products which has so-so/predictable first period, but across its lifetime they maintained their demand (different segments buy at different time, in different location).
There are also products which has superb first period, but unable to maintain their demand across its lifetime (segments who wanted it the most already bought it, and other segments are not interested).
The last volume of Naruto managed to sell about 870k copies in its first week, but the second week drops significantly to be barely 180k copies. By ratio, that was a very huge drop. And when you compare to the historical sales of this franchise, you'll never see so much drops in the second week. People who followed this series for long time can relate...
So, don't judge too quick. Let's wait and see...
Well, Is this enough to convince you.
Japan DVD/BD yearly sales 2013 (December 2012 - December 2013) : http://www.someanithing.com/591
Road to Ninja only had 18,890 total DVD sales.......As for BD sales, It's not shown (but it's not greater than the DVD sales)
It seems that the Last already supassed RTN's total sales in 2013 in just a week.
Edited by HuskyLover, 28 July 2015 - 04:55 PM.