CoD MWIII's campaign is a large bag of trailmix.

the linear missions vary heavily. some are tight, slow pushes into enemy lines, killing as many as possible for a chance to be able to move ground. while some are boring walks forward, into enemies that are either nothing, or bullet sponges

open missions are the same type of deal. some are boring shooting galleries with more loot than there are enemies.
the open missions strive when they're slower, and let you breathe, and sit with your thoughts and choices.
but with unreadable stealth mechanics, and enemies constantly flooding down on you when you're found, these high moments become rare.

for the story meanwhile, it's biggest flaw is that it isn't finished. it gets you invested with so many stakes. all the civilians that are lost, Soap's death, and Makarov being so brilliant.
although i do wish that it manifested a little more on the public opinion side. the plane mission is so brilliant at making you feel so hopeless, but i wish it had real consequences in the story.
if it manifested in a satisfying death for Makarov, these stakes would feel like sacrifices. but the cliffhanger makes it all feel more like a death march.

gameplay gets a 3/5 - some real promise, with some flaws on top of it.
story gets a 3/5 - more could be done if the stakes were more fleshed out, and if it didn't end on a cliffhanger.