Activision has a lot to brag about with Destiny the top-selling new IP of the year, Skylanders the top-selling kids game, and Call of Duty: Advanced Warfare the top-selling game. But there is a factor that seems to be worrying the COD franchise. It seems that Call of Duty is hitting a downward trend, even though the latest game received a pretty warm reception. According to analyst Michael Olson Call of Duty: Advanced Warfare has seen US retail sales decline 27% from Ghosts in 2013. Ghosts itself declined 19% from 2012′s Black Ops 2, which itself dropped 17% from 2011′s Modern Warfare 3. “This is disappointing data following first week Call of Duty: Advanced Warfare sales showing a year-over-year increase,” Olson said. “NPD data does not include digital copies or international sales...