Sorry... best you can do is add them up yourself
http://vgchartz.com/games/index.php?name=Madden+NFL+08&console=®ion=All&developer=&publisher=&genre=&keyword=&boxart=Both&results=50&order=Hits
However sales are not always complete, for instance it is rare there is any PC data at all, and or Madden in particular there isn't any Europe data (assuming it's released in Europe?)
We can bug Talonman if you like to get him to add a "total" figure at the bottom of the table in link I gave.
If you want compiled games data though I think it would be a job for ioi.
Perhaps someone could make a suggestion to have a kind of tool to compile data for multiple games (say 10 at once) so you could pick and choose games and there would be various ways of viewing the data for those games.... that way you could pick out all the versions of Madden for it.
