Whereas Battlefield 3 boasts a new engine that gamers are raving about, Call of Duty has made do with a modified, ageing IW engine - version 4.0 was used for Modern Warfare 2.
So what about this autumn's Call of Duty game? Has Infinity Ward - rumoured to be co-developing with Sledgehammer - gone back to the engine drawing board?
Doesn't sound like it.
"That would be counter productive," tweeted IW community man Robert Bowling. "An engine takes years and years to develop and get right."
In March 2010, Infinity Ward was torn by the sacking of studio bosses Jason West and Vince Zampella. Their departure leached ranks of loyal staff. But Bowling stayed put, tweeting that, "I work at Infinity Ward and plan to remain here. We've got a great team and working on a great project."
When Activision will lift the lid on this autumn's big new Call of Duty game is unknown. Is a summer reveal at E3 too far away?