I'm a fan of Left 4 Dead, so I may surprise you a bit when I agree with you. The maps in L4D and TF2- and in a lot of ways, HL2 and its episodes- are more designed to be movie sets than tactile locations; while they look great and convey the atmosphere well, there's no real sense of being there, no need to study the environment and identify all its nuances. With L4D, it's because the Infected don't shoot at you, and the maps are basically designed to be obstacle courses; with HL2, it's because combat is pretty straightforward, and Valve's design decision to have the player rely primarily on the gravity gun requires relatively uncomplicated level architecture.
Contrast that with games like Rainbow Six and Gears of War, where simply standing out in the open and shooting is going to get you a severe case of lead poisoning pretty quickly. There, you have to be much more aware of the obstacles around you, and make quick decisions about where to move and what angle of approach is best. There's a more visceral feel to it, as though the game world itself is an opponent actively trying to defeat you.
That's not to say that Left 4 Dead doesn't at least approach the concept. There is a need to keep your head on a swivel at all times, watching for areas from which the Infected can approach, like gated roadways or blind alleys. Closing doors behind you is vital for blocking their progress at least temporarily. Still, I'm rather upset that you can't form makeshift barricades from available objects in order to block likely avenues of attack.
So which approach is better? Neither. It's different styles of gameplay. I liked the cover system of GoW- in fact, it was about the only part of the game I liked, aside from the rain effects- but I simply can't picture Zoey slamming herself against an overturned wreck of a car and blind-firing into a crowd of Infected. Sometimes it's more fun to be a walking bullet-hose and let the action take center stage.