I haven't played Doom yet, but the main contenders for best modern shooter campaign is generally Wolfenstein, Doom, and now Titanfall. The weird thing is, I enjoyed Wolfenstein but never really felt it was a really -great- campaign. It was good enough, fun, and very lengthy. There's a lot of meat to it, and I guess that surprised people, because no one really makes a big long single player only FPS anymore. But the game had so much fat, and I felt a lot of it went on for longer than it needed to. Stages are large but not always interesting. There is a lot of combat but a lot of it also feels samey. Uncharted games also have this problem, where it's not the game design that's really driving what makes people love the games so much as the story and characters and just there being so much of it.
Titanfall is a totally different beast. It's the sort of campaign that is game first and story second, but every step of the way is designed to be a -single player- game. The sort of game experience you have alone, rather than with friends. But totally a game - and a great game. It's like a modern Contra or Metal Warrior, except with more variety and really great production values. It's short but never overstays its welcome, and the stages are unique enough that you can imagine yourself going back to replay them just to get that slice of gameplay again.
I have no qualms with saying that the Titanfall campaign is representative of what I feel more shooter campaigns should strife to be. Not story vehicles with the expected gameplay, but vehicles for gameplay we don't get in multiplayer with interesting story flavoring. Titanfall 2 is to first person shooters what great Platinum Games titles are to character action games.