I think it'll have a more enjoyable campaign than your typical CoD and BF affair, even if it's not hugely innovative.
I put the series on the same level as Gears when it comes to enjoyable single player campaigns. Of course that series has co-op, but overall they tend to be rather linear roller coaster rides. As I've said before, these games aren't Last of Us quality when it comes to that, but in the FPS/TPS genre there's not much high-bar competition.
Shadow Fall looks a lot more interesting to me than the previous Killzone single player campaigns were, simply because of how open the environments are now and the addition of more tactical elements and open mission objective structure similar to Goldeneye. I think the single player could surprise a lot of folks because it sounds like they're holding back on releasing a lot of info.
Of course the main reason I'm even getting KZ to begin with is for the multiplayer and they haven't even shown it. Its chances for success will mostly ride on how that mode turns out.