You just listed a bunch of games (in and out of a genre, even) that are not exactly similar to each other. The case presented by "a lot of people" is highly vague and doesn't even examine what is distinctly Japanese or Western. As such, you ignore the possibility that Resident Evil 6 was inspired by other Japanese TPS (e.g. other Capcom games, such as the evasion dodge-centric Lost Planet and the previous REs that have many of the same concepts (including parallels from things such as now discarded QTE counters). Vanquish is easy to draw parallels to with how dodging into a shooting stance works. Or how about Demon's Souls as it features player invasions - though campaign crossovers is more unexplored territory). I would better describe this as "Capcom influence" (if not plainly a "Japanese action game influence"). I believe you can see this influence in games like Dragon's Dogma, which some would say is just a Elder Scrolls clone if they weren't paying attention. That elaborate (over-elaborate, some could argue) combat system design is just in their basic design philosophy. If they really wanted to make a standard western TPS, they could have halved the mechanics in there and dropped the enemies designed around them. It doesn't make sense to do the extra work that only makes the game look increasingly different than other franchises.
As things stand I believe it is fair to say it is more than an amalgamation, or at least no more one than every single other contemporary game. You could make any one look like one thanks to assigning every single mechanic to a bunch of individual random sources (which is exactly what one does when they pull out a big old list of games like you did). If you want to prove it as nothing more than an amalgamation then you need to not only be highly specific, but also find a way to exclude most other games to make that statement meaningful.
I can say for certain RE6 doesn't play pretty much at all like a Call of Duty game and if a lot of people want to say it does, then, unsurprisingly, a lot of people don't know what they are talking about. (It is also more than a little bit funny to imply Resident Evil 4 as one of the games that inspired Call of Duty.)
The fall-from-grace narrative you would entertain yourself with as written in your last sentence is a bit nauseating. I don't know what to do with that kind of lamentation. A game being inspired by other games isn't really noteworthy (nor is a Resident Evil being inspired any different). None of the games inspired by RE4 are less for it; I would say the contrary. The idea that RE6 is nothing but recycled ideas is easy to reject as it ultimately stands out as a relatively fresh take on the TPS genre and pointing out that you can find a TPS from the west (this matters, I guess) that does one of the things it does (IDK, uh, dodges, but only the idea that it has dodges, not exactly RE6's dodges and how they interact with enemies) doesn't really change that. We already know what the Gears/Mass Effect 2+/Uncharted (slightly less so)/etc. cover TPS formula looks like and what the ingredients are there (even if they can be changed and updated for each game), and RE6 looks very little like that. In any case, spare me the silly sentimentality over videogame history. It is, if nothing else, highly unnecessary.
What an overly-verbose misreading of my post. I never implied that taking influence from other games was a
bad thing, that was your assumption. Everyone does it, in every culture, and it's a healthy part of the creative process. So you don't need to be so weirdly offended by the un-controversial notion that Japanese and Western developers influence each other
Which is besides the point, as Resident Evil 6's problem wasn't in it's influences, but it's execution.
EDIT: But since you wanted me to be more specific in drawing comparisons:
Call of Duty: Half the people reviewing this game compared the game's spectacle, emphasis on explosions, shooting, QTE button prompts and globetrotting campaign to
Call of Duty and Michael Bay. It's not one that I personally agree with, but it strong enough for many people to draw comparisons. It's not like Capcom is the only Japanese developer to take cues from CoD recently. Also the new perk system and increased emphasis on multiplayer matchmaking
Left 4 Dead: The companion "downing" mechanic where one player gets knocked into a fight for your life mode while the other must pull them back up. Also, the specialized zombie designs in Leon's campaign. The Whopper (boomer), the Screamer, and a couple of particularly inspired sequences in the first two chapters. Notably the one where you must fight through a graveyard, run up to a chapel, pound on the locked front doors, only for the paranoid occupant to refuse to let you in. So he starts ringing the church bell and you must fight off waves of zombies until he lets you in.
Dead Space: Mostly the UI elements. Menus that float in front of your character while they can walk. Also a single button that can now push to reveal the glowing "rail" you must follow to your next objective. Come on, this is obvious.
Gears of War: I haven't played these games, so bear in mind I'm going by hearsay. But pretty much any game that incorporates a cover mechanic gets compared to GoW. Unsurprising, since it was the first game to really popularize the mechanic in TPS games.