Both Halo 2 and Halo 3 have also beaten the last Final Fantasy game in sales. Final Fantasy is on a decline, saleswise. By the time it hits the market, Halo 3 will have sold close to, if not more than, 7 million copies, and I have doubts about FFXIII getting that high.
Thinking Halo will outsell Final Fantasy does not make me an Xbox fanboy, btw. I have plenty of love for Sony, just a differing opinion from yours on the selling power of FF currently.
Threads of Interest:
The Movie Thread: http://www.vgchartz.com/forum/thread.php?id=6880
The Crow Eating Thread: http://www.vgchartz.com/forum/thread.php?start=0&id=3886
The Betting Thread: http://www.vgchartz.com/forum/thread.php?start=0&id=7104
Custom GIFs Thread: http://www.vgchartz.com/forum/thread.php?id=18963
The Greatest Game Ever Conceived On Any Platform
Tag: "I have tasted Obi-Wan's bitter tears"