I'm currently replaying RE4. Man, this game. It's even better than I remembered — and I remembered it being one of the best games ever. It really is!
I love RE1, RE2, RE3, RE4, RE5, RE6, Revelations 1, Revelations 2. I would probably enjoy CVX, as well.
So I'm not hating on other games when I say I love RE4 best. They're all great.
But yeah, RE4 really is exceptionally well-made. The journey is impeccably paced and consistently introduces new ideas from start to finish. Each idea is well-designed and effortlessly introduced with just the right balance and learning curve. Each idea receives just the right amount of repetition and iteration, and no idea overstays its welcome.
I also like how each set-piece tends to have a few less enemies than you'd expect. RE4 errs on the side of "less is more," and it works. It generally throws something at you twice before moving on, which is perfect. And between each set-piece there are many small moments that are satisfying, like the occasional light puzzle or divergent path, i.e. backtracking across the lake to see the dogs and swamp village at night or visit the merchant in the cove, instead of going straight for the dam and waterfall.
RE4 is a game where I enjoy, like, every single beat, be it gameplay or storytelling. I love all three regions and every area therein, and all of the encounters. Just a masterpiece through and through. Probably my favorite game ever, and my current play-through reaffirms it.
But like I said, I'm not trashing other games by saying this. I feel the need to point this out since the RE community seems a bit toxic in this regard, i.e. most people can't say they like one game without hating on another. :-\