sundin13 on 15 October 2014
Just for fun, I plotted the series sales over time using Capcom's data as of June 30, 2014 (newer titles will have sold more over the past few months, but I am ignoring that for now). I also decided to add the best fitting line I could, although with the high variablity between games, it doesn't quite show the most accurate picture. As a note, '09's release was Wii exclusive while all other titles were on handhelds:
Excluding the first two values does decrease the slope, but the slope is still not negative...
Make of it what you will...