Obviously a gaming company is more interested about revenue (and even they care only about the revenue gained from selling games to retailers, not the revenue shops get from selling to consumers. And they don't need a tracking site to determine that, because the money is sitting in plies at their feet)
But if you compare revenue, then you're charts are more biased towards expensive games such as Guitar hero, Wii Fit, as well as modern games (Unless you take into account inflation somehow, but that sounds much too complicated) It is also not really valid for VGChartz, because fluctuating exchange rates mean that two Japanese made games that sold the same quantity at the same price would have brought in different revenue.
Sales rather than revenue is simpler to calculate, easier to read, and more useful to everyone