Joshua, what a great description of the franchise.
I´ve played CoD1, 2 and 4 in PC, and the single player was well executed, but the visuals were not mindblowing. Lot of scripting, but (as you said) "intense" action. Really really good movies. I remember the time when a WWII shooter game always had a sequence taken from a WWII movie, e. g., MoH:AA had Utah Beach from Saving Private Ryan and CoD the Volga crossing from Enemy at the Gates. CoD franchise continues that trend.
In fact, I perceived the short duration of CoD4 as a positive thing, from the "movie" perspective. A longer campaign becomes repetitive, because the mechanics that build the experience are clearly obvious. In my case, that prevents a second playthrough. All seems to be "seen", too streamlined, a bit boring and artificial. But what a first play.
MP is a totally different thing. The mechanics that make you feel confident in the campaing (fast handling, good control, precise shots, ironsights, and, in console, smoothness) are there too. You start and the reward is inmediate. All seems to be in place, maps, weapons, klling is accesible. Great comparison with CS. I die, but I kill as well, I feel "dangerous" even being a rookie.
The offer is clear: a bright movie done with archaic, albeit effective methods, and a excellent multiplayer with a lot of life, long lifespan, and the bonus of a massive hype and marketing campaing. Bundles, community, prestige... all is in.
The phenomena of the generation in the HD department.
And excellent job of the developers.