This one's for either Wombat or Cheapy.
With the November sales numbers in, we see that sequels or yearly-releases in a franchise, such as Madden '09, Gears of War 2, and Call of Duty: World at War have sold millions of units each. New IPs, however, have struggled to sell any number of units, with Dead Space selling only 421,000 copies, Left 4 Dead selling 410,000, Mirror's Edge selling a paltry 145,000, Little Big Planet a shocking 141,000, and Valkyria Chronicles a scant 33,000 copies. My question is, why do you think these games didn't sell well? Was it the time they were released, the economic situation, the quality of the title, or were people just not interested?
Personally, I find it depressing how many people berate EA and Activision for releasing nothing but sequels and yearly-iterations in a franchise, but rush out to buy them and ignore new games that are trying something different.