Why Capcom ditched horror and went action heavy for Resident Evil
Looking back at the history of Resident Evil, you can see how the series rose, arguably peaking with the fourth chronological title. The game finally abandoned the series longtime preference for pre-fixed camera angles, and tank-like controls, switching to an over the shoulder view, which improved aiming, character movement, etc., and the gameplay experience overall.
But if you look at the chronology, of the games that received critical attention, sandwiched between Resident Evil 3: Nemesis, and Resident Evil 4, you'll notice the GameCube remake of the original Resident Evil. A lot of people will consider the series' downfall beginning with RE 5, and culminating with RE 6, but according to the series creator Shinji Mikami, the downfall actually has roots in this remake.
Despite rave critical reviews (the game currently boasts a 91 from Metacritic and cracked "best horror game" lists and a wide array of outlets, magazines, etc.), sales just weren't up to snuff for the title. Despite selling over 1.3 million copies by Capcom's own reckoning, Mikami and the company were still disappointed. You have to remember that around this time, that the RE series was languishing, with titles like RE Gaiden, Survivor, and Outbreak certainly not helping the brand.
In an interview with IGN, Mikami explained that as a result, he "decided to work more action into Resident Evil 4. Resident Evil 4 would have been a more scary, horror-focused game if the remake had sold well." From there, it seemed that action was the way to go, and that's what was injected into the games more and more, until, ultimately, you wind up with an overreaching plot that sends protagonists halfway around the world to fight what amounted to a bizarre dinosaur, formerly an advisor to the President.
With Resident Evil 6, producer Hiroyuki Kobayashi told 1UP that Capcom was "trying to be as inclusive as possible. We're trying to reach as many people as possible...That makes it hard to maintain a horror feel to it when you're trying to be inclusive. It is a challenge. I'm not afraid to admit that. We're trying to see what kind of action we can include in the game and still maintain the horror sensibilities. Trying to blend those together is not an easy thing to do."
Thankfully, Mikami is looking forward to greener, more horrific pastures, working on a brand new IP with Bethesda, The Evil Within. As for Resident Evil? The company hopes the next RE game can return the series to its roots, and ported Revelations to consoles as a sort of trial run, but as of yet, Capcom has provided no other plans or ideas.