They're right that games are about gameplay, but this is like saying that action movies are all about the car chases and explosions. Most action movies are vehicles for stunts and destruction. But the story is there to make those stunts and fireballs matter. The story gives the action weight and context. An action movie that was two hours of nothing but disconnected footage of car jumps, crashes, and exploding vehicles would be wearisome to the extreme. I don't mean to go all MovieBob on you, but fights are a lot more interesting when we we care about the people in the fight and we understand why they're fighting. We might be here to see some spectacle, but the story is there to give those moments tension and emotional heft. It's no different with videogames.
Whenever I bang on my "this story sucks" drum I invariably get someone asking me, "Why don't you just go watch a movie if you want to see a story so bad?" Which seems to imply that you shouldn't expect good stories from games. But if you think videogame stories have to suck, then you've been playing the wrong games. KOTOR, Jade Empire, Thief, Prince of Persia: Sands of Time, Max Payne, Sonic Unleashed and the aforementioned Left 4 Dead all manage to deliver both engaging gameplay and a well-written story.
But the "go watch a movie" taunt overlooks an important point: If the story doesn't matter, then why do game designers waste so much time on them? Why do game designers keep putting horrendous stories in their games if they don't want to tell a story in the first place? I understand that good writing is hard. Not everyone can do it. Constructing a story with a compelling arc, a solid foundation of backstory, and believable characters can be a complex task. Weaving that tale into gameplay is an additional challenge that moviemakers don't have to face. I understand that there just aren't a lot of people up to this level of challenge, particularly since most game designers began as programmers instead of writers.
Have a lot of story in your game, or don't. But whatever you do, don't just put in story because you want to make a movie where the player steers the camera and decides who gets shot first. You can see this evident in games like Resistance, anything by Epic, Resident Evil, and a host of other generic shooters where reviewers have to apologize for the story before they can tell you how fun the gameplay is. (People keep telling me that Resident Evil is supposed to be a send-up of classic horror movies, but I don't buy it. In order to be a "send up" it would have to satirize the originals, not simply duplicate their stupidity. And in any case, "farce" and "tension" go together like marshmallow fluff and entrails.) These games could be more fun if the writers said less and left more to our imaginations.
Sure, I'm a story snob. Not because I demand that all games tell Planescape: Torment-level stories with Shadow of the Colossus-level emotional impact, but because I demand that if a story is in the game, it should be worth seeing.
(Also, I was just trolling you with Sonic Unleashed. Let's see if anyone ragequits the article and comments without reading all the way through.)