Sales of Call of Duty: Black Ops 2 are on a trend to be down 15 percent from last year's launch of Modern Warfare 3, financial analyst Arvind Bhatia of Sterne Agee posits. Modern Warfare 3 sales were down 5 percent from the previous year's Black Ops, and if this scenario plays out again Bhatia calls it "a cause for concern" for Activision-Blizzard.

Call of Duty as a franchise is responsible for up to 45 percent of Activision's earnings before interest and taxes, Bhatia says, justifying the concern clause. Average reviews of Black Ops 2 were lower than Modern Warfare 3's, and Black Ops 2 launched a week after Halo 4 but a week before Black Friday, meaning some customers may have waited to buy it, Bhatia says.

Sterne Agee downgraded Activision's rating from "buy" to "neutral" and reduced 2013 estimates from $4.74 billion to $4.3 billion.

All this is in spite of the fact that Black Ops 2 pulled in $500 million at retail on its first day, breaking records and surpassing Modern Warfare 3's $400 million, and is the UK's fourth largest launch ever.