When people say that the easly best game in the series is its downfall I tend not to pay attention to them

I blame the death of Clover Studios. That stupid move caused a lot of Capcom's best talent to leave. Clover could have very well been the ones to make Resident Evil 5 and 6 had Capcom not axed the studio. 

That being said, I feel that Resident Evil 4 is the singles best Resident Evil game to date. It updated everything that needed to be updated in the series while maintaining some of the horror elements that the series was known for. It was Shinji Mikami's passion project and it shows. What killed Resident Evil and Capcom in general was Capcom's management. The caused all their most talented people to leave and instead of innovating like they did with Resident Evil 4, they started to (poorly) copy others and Resident Evil 6 is the result of that. Capcom doesn't seem to understand that just because Gears of War and Call of Duty have better sales doesn't mean survival horror is dead. It's kind of like how Square-Enix was surprised by Bravely Default's success because they though traditional JRPG's were dead for no reason.

How can you blame RE5 when RE5 is better than RE4 outside of Sheva's AI? :P

i blame paul w.s anderson and mila jovovich for making those awful resident evil movies.

Considering the commercial success of the movie, Capcom was like "lets make the games like the movie"

The downfall for what you thought RE should be maybe. But critically, and sales wise no.

RE5 is a very good game, that sold well and was critically acclaimed. it's just not scary. It's a more actiony version of 4 with better action. But worse atmosphere.

It's definitely a co-op game with Sheva's terrible AI. So if you don't like co-op the game isn't near as good.

One game that has issues (RE6) does not a downfall make.

Well, it actuallly did influence RE6 a lot more, you're right about that. RE5 came out on 2009 which was when CoD was really picking up steam.
RE5 actually had good scores, but it departed really far from horror at that point, much more so than RE4.

I know. I was going to put a but was rushing because it was late...

In the end, it was Capcoms fault for the overly high expectations & for jumping to conclusions that people must not like horror.

Yeah because RE3 and RE0 was sooooo loved by all RE fans.../sarcasm

The gameplay of RE4 was great. They just screwed everything else up. Alien parasites? Cult history? President's daughter? Napoleon? Come on!

I blame Canada.