Going with what was said earlier about Leon's campaign, I think his campaign was the worst. Not to say it was bad. It's like a well-done steak when I prefer medium lol.
NPCs were too disposable in his chapters, and like someone said, Leon and Helena were honestly bad luck from beginning to end.
Also his story took him through settings I can't describe outside of using the word 'setpieces'. Another earlier post makes a better note of this with the appropriate spoiler tags. They weren't used with the same satisfying flow as they did with Jake's. Perhaps it's because Jake's made sense within the context of his and Sherry's situation.
Chris' was my favorite campaign. Despite certain badly implemented events, everywhere Chris was and everything he did made sense. People complain about his campaign being a straight up third person shooter with the awesome RE6 acrobatics, but considering he's a BSAA jarhead fighting bioterrorism on the frontlines, it would be unusual if he wasn't in a literal warzone against the J'avo.
Chris was also my favorite character throughout this whole C-Virus ordeal due to his personal vendetta steadily getting in the way of his job to the point where he nearly becomes irrational. Piers balances him out, and it's visible in Piers that taking Chris' recklessness is heavy on him. The two have good chemistry that's suitable for them. They aren't the fun and teasing Jake and Sherry, but they're not trying to be.
I have no idea what was going on between Leon and Helena for the entire 5 chapters for Leon. At first, I thought the awkwardness between them was funny, but then realized it was serious upon Chapter 5. Capcom dun goofed in Chapter 5. I can't even look at Leon the same way in RE4 anymore.