Its well documented that Cliff Bleszinki was inspired by Kill Switch and the same guy who deisnged kill switch also worked on gears. You dont have to acknowledge what Gears and Epic has done in gaming, but people and devs know. This is why i said time after time, "popularized"
Here is an article on how Gears of War changed gaming that explains things pretty well http://www.g4tv.com/thefeed/blog/post/712864/how-gears-of-war-changed-video-games/?cmpid=sn-110418-facebook-28-fbfantrack
The concept of cover goes back almost as far as video games. Just think about hiding from Eggman under a platform or from Bowser behind a stone. This carried, naturally into almost every action game that involved projectiles. Metal Gear Solid 2: Sons of Liberty was one first games to use a modern cover system in which the character could take cover behind walls and crates and peek out to shoot enemies. Similar systems were implemented in Winback and the Time Crisis arcade series, but it was Kill Switch, Namco’s surprisingly mediocre third person shooter that changed how shooters were designed from that point forward. Kill Switch was the first game to use cover as a main gameplay mechanic. You could vault over walls, blind fire, and use one button to slide into cover. It was fun and fast paced, if a bit too heavy on the cover aspect and too light on everything else. But Epic Games took notice.
Lee Petty at Epic showed Kill Switch to Cliff Bleszinski, and they both thought it was perfect for Gears. Indeed, only a short time after Kill Switch was released, its lead designer, Chris Esaki became a design director for the original Gears of War. With his help, the team at Epic spun the raw potential of a cover-based shooter into pure video game gold. Gears managed to improve on the mistakes of Kill Switch by creating a multifaceted game that still used a cover system at its core. After proving that it could be done and done well, myriad games began to incorporate cover systems; either on a small scale like in GTA IV or on a larger scale similar to Gears; like in Army of Two. Even Star Wars: The Old Republic is going to offer up a cover for their Smuggler class. But no matter what game presents a new cover system, the question always remains – how does it stand up to Gears of War? In this sense, Gears has become the gold standard for cover systems.
Gears of War did not introduce anything that hadn’t been done before in video games. It simply picked out some neglected aspects and did an incredible job of improving them, and meshing them together in a way that really worked. Everyone had played a co-op game before Gears came out, but no one had really cooperated in the way Gears forced them to. In fact, it wasn’t until Portal 2 that my co-op buddy and I felt a challenge similar to Gears of War. Everyone had used cover in games before Gears of War, but no one had blind fired, slammed into walls or mantled over obstacles quite like they did in Gears. And while Survival Wave Combat© existed in one form or another before Gears, it has never been the same since.
There is more on the article in the link