I even just looked it up. The first game to implement a cover system like Gears has in a 3D third person shooter was a game called Winback for the Nintendo 64. Players could not move and shoot though, they had to take cover before they could shoot. It was later refined in Metal Gear Solid 2 by having cover as an optional means, but also having enemy AI use cover. In the end, the only thing Gears really did for the cover system in 3rd person shooters was make environments developed specifically for that and having one button used for going into cover. With the core of the cover system already developed, it was only a matter of time before someone implemented it. Using this line of thinking, Uncharted 2 (which I do agree with being on the list) should be given just as much credit for have a vertical cover element with being able to hang from the environment. I've played Gears. I didn't have much of an opinion of it one way or the other, as it was a good game with promise, but any promise it had was dragged down by the ridiculousness in the characters and gore. The two things balanced each other out for me. I enjoyed the gameplay. But I'm not going to give it credit other games deserves.
It seems you keep on mixing up influential and important. Influential is affecting how other games and made and other aspects put into them. I'd agree every game on this list is influential. But important? That means it is something that needs to be done or experienced by people or was a major shift in history. Not in how games were developed, but in the history of gaming.
Grand Theft Auto 3 is important I agree, because it shifted the public's view on games, largely in a negative direction. Wal-Marts finally started checking IDs for age when selling M games, and it was an overall controversial game. It's an important point in gaming history, even if someone plays it and thinks it sucks.
Resident Evil 4 is important, because it was the the catalyst for the near-death of the horror genre that Resident Evil 1 brought to the world of gaming. It wasn't until Dead Space came out that the genre was breathed new life.
Knights of the Old Republic, it made a big name for Western RPGs, and combined the concept that tabletop RPGs had of a d20 with the existing RPG format. Sure, Neverwinter Nights and some other games had been Western RPGs before KotOR, but KotOR was what put them on the map.
Devil May Cry, I will admit I can't really say anything on as I never played it or payed much attention to it. It's something I want to fix sometime when money and time allows.
The reason I did put down Kingdom Hearts, was because it was, in essence, the first large cross-culture, cross-media, gaming experience. It combined the American-based Disney properties with the Japan-based Final Fantasy property, giving something that could appeal to Japanese and American gamers and non-gamers alike. It was also the first time putting together game worlds with movie worlds in a video game. Sure, there had been movie-based games before, but not a game with both things from games and movies together, if that makes sense.
So see, there's things that are influential, and then things that are important. They should not be mixed up though. I'm not wanting to be a jerk, I just am a stickler for that sort of difference, especially in gaming, because as someone who wants to get into the industry, I want to make something important eventually, not something influential. And I wouldn't want something I made that just had some influences on other thing being called important over something truly important, same as how I wouldn't want something important I made being overlooked for something influential being called important.