Finished all four campaigns, unlocked all files and figures, and unlocked all Mercs costumes... This game is amazing. Feeling bummed there's not more content to explore, though I feel greedy saying that since this game has so much packed into it.
I think the Chris campaign is my favorite, closely followed by Leon and then Jake, though Jake had one of the best chapters in the form of Ch. 3. Ada is the most fun character to play as (and easiest on the eyes!), and her campaign was consistently fun, but somewhat secondary to the others (which makes sense).
I'm surprised how fun it was to revisit the first two chapters in Chris when I was hunting for emblems; now that I have the mechanics down pat, the first two chapters really shined in terms of gameplay, and because I felt more in control I was better able to appreciate the environment and attention to detail, which is lovely. I already loved the last three chapters in Chris, especially the setting and boss of Ch. 5, so I guess overall his campaign is my favorite.
But like I said, Leon's is close. Once you get past the slow start to Leon Ch. 1, the bulk of the first chapter and all of Ch. 2 is amazing. Ch. 3 is great too, aside from the brief swimming section. (Swimming was much more fun in the Ada campaign) Leon Ch. 4 was decent, most notable for its start. I really liked Leon's final chapter -- I thought all of the boss battles were fantastic.
Jake's campaign was most uneven, but still decent, all in all. I was meh on the first chapter and remain so. The first part of the second chapter tests my patience, but everything past the snow storm is golden. Jake's Ch. 3 is possibly the best in the game, as I already said. The fourth and fifth chapters had their moments, especially the final boss fight in the fifth chapter.
Ada's campaign was surprisingly interesting. The all-original setting in the first chapter, as well as the emphasis on stealth and turret exploitation, was quite interesting, and the swimming mechanics finally delivered here. The puzzle was simple but interesting (and creepy!), and the free-running section, while full of cheap deaths, was oddly addictive ("Just one more try!"). The rest of the campaign was fairly interesting, and the boss in Ch. 4 was awesome.
I'm eager to replay some chapters in online co-op. No idea which one I'll start with, though -- hard to pick a favorite!