Call of Duty is short, multiplayer-focused, and compares horribly (at least in the eyes of us PC gamers) to more modern designs like STALKER and Crysis. Yes, both Half-Life 2 and CoD are linear, but there's a world of difference between the two in every other area...
When Half-Life 2 came out, immersion was something new, and Half-Life managed it beautifully, marrying old designs (corridor-bubble, as I'd call it, with small, yet open areas of exploration and combat married to more linear corridor segments) and new ideas (no cutscenes, player agency all the way through) over a 14-odd hour singleplayer experience.
In contrast, CoD is a straight corridor. The only "open" areas are basically shooting galleries, each with exactly one entrance and one exit, the latter of which will probably be held open for you... heck, it's even divided up into missions with debriefings and loading screens in between. it successfully brought the hollywood blockbuster to videogames, capturing both the good and the bad of big-budget films. But that style of games has reached the limit of its appeal.
STALKER, Crysis, and a few other games have created what I would call the "bubble" FPS genre. No (or few) corridors, no fellow soldiers opening doors for you... you enter a map, and you can go anywhere in that map you darn well please. It's a revelatory experience, akin to the difference between playing (say) Dragon Age 2 and Skyrim. It represents a promising potential future for a once-again-stagnant genre, which is currently chasing its own tail around that same, tired corridor model of gaming.
So what am I saying? There should be room for all three brands - immersive, passively-guided experiences; movie-style, actively guided shooting galleries; and huge open-world playgrounds. But right now, only one is being made in any significant quantities - and that is causing a great deal of resentment.