RE4 is the series finest hour for me, definitely one of my top 10 games EVER(maybe even top 5). Yeah, it did change course from RE1-3, but the series was ready for change, and I thought RE4 made the perfect improvements to the franchise that where needed at the time. Sadly, although I found RE4 just about perfect, Capcom continued down the path of "change" and just about ruined the franchise with RE5-6.
Where we could all debate the "survival horror" gameplay of the RE1-3, with the more action specific play of part 4, the one thing I think any true fan can agree upon, is that RE is a "single" player experience, PERIOD. Once the co-op gameplay was added, I was gone and won't be back until some form of the games roots are returned.
We can all see how Capcom is currently in the financial "doghouse", and when they moved RE in to what they though fans wanted, they made a huge mistake, as they really had no idea how the series could best be moved forward. They just went where the money was. EA did the same thing with DeadSpace, as both of these games where great because they where unique to the market. Once you try to make them like every other mutiplayer action game, you kill the core audience, and market you are now trying to get, could care less as these games are poor substitutes for what the best sellers in that genre actually are.
RE4 will always be my favorite of the franchise, and looking at Capcom's current situation, I'm sure it will be the way indefinitely.
Chris