Activision puts out a new Call of Duty game every year. It's been that way for the last half-decade or so. Trouble is, this annualization give people a wide-open lane to complain about recycled engines and how the games all look the same.
Mark Lamia—head of Treyarch, the studio behind the Black Ops branch of COD—knows all of this and wants people to know that some the software powering the sequel won't be a complete overhaul of the tech used for 2010's Black Ops. In an interview with Activision blogger Dan Amrich, Lamia says:
Engines, each time they get touched, they change. The creators alter them; they don't modify what they don't need to, and then they alter what they need to. You can't make a competitive product if you're not upgrading that engine along the way.
So what specifically got touched? Graphics and lighting, it seems:
I think what people are asking for is for us to push. They want us to make a better-looking game; they want things. I don't think those are things people can't ask for. We asked ourselves that very same question - we wanted to advance the graphics. I think the questions are valid. The answer may not need to be an entirely new engine, but you might need to do an entire overhaul of your entire lighting system. The trick is, we're not willing to do that if we can't keep it running at 60 frames per second - but we did that this time. So this is the Black Ops II engine.
Mark Lamia discusses the Black Ops II engine
[One of Swords]