I define horror or a horror game as a game that scares you or at least tries to scare you, has a creepy & tense atmosphere, a sense of helplessness, etc.
RE6 is filled with explosions, gunfights, flashy things etc, you're platoons of soldiers, government agents and mercs in a
WAR.
RE6 has zombies, ugly monsters and mutations, one-hit-kills, stalkers that just won't die, jump scares, dark and abandoned places, insane villains, violence etc
So does loads of action games, Left 4 Dead, Gears of War, Dead Rising, Last of Us even my favourite franchise Duke Nukem has those things. They're not horror games at all they're action games.
Doom 3 is a good example of how you can mix horror with action, sure it was more of an action game, but it was dark, creepy, you're all alone with monsters creeping around and sneaking up on you, sudden load noises, lights going out etc, it was scary even though you were armed to the teeth in firepower.
RE6 & RE5 had no horror what so ever.
I don't know where you got jump scares from in RE6, those parts in the start of Leon's campaign are not jump scares, they were just desperate attempts at jump scares, NO ONE jumped at them.
The Evil Within is 100% a horror game for sure, it's creepy, it's scary, it's dark, you're all alone, there's shocking and tense moments, just like Outlast and even the upcoming Alien Isolation.
They are what I consider horror games.