Content may not be sacrificed, but meaning is. Why bother with a version of a piece of art that is far and away from the author's intentional meaning? Graphical fidelity has a larger meaning here than just pretty pictures.
What's lost is the immersion factor. Modern Warfare was so good on 360 because it was so immersive, due to its incredibly lifelike visuals and sound design. Its controls were tight and it had some minor design innovations, but its true raison d'etre was its visceral delivery of the combat experience. It eclipsed everything up to that point.
Take that away, and you don't have much.
Eclipsed everything? Someone obviously didn't play the previous 3 CoD games. Also Crysis blows it away in visuals, and innovations. I get sick of people forgetting the Cs oD series existed in a similar form on PC long before it was, gimp..., I mean ported on consoles. I loved the series at one time but i grew tired of it right around the time it became the cool thing to think it was the bestest game ever.