I'm just checking, but you are holding Fincher's debut
Alienł against him but forgiving Cameron's
Piranha II: The Spawning?
Throwing out Cameron's low-budget debut he has directed only eight features:
The Terminator, Aliens, The Abyss, Terminator 2: Judgment Day, True Lies, Titanic, and
Avatar - with a slew of
Avatar sequels coming. Plus a couple of documentaries. But eight narrative features in thirty-seven years. With
Mank Fincher now has ten in twenty-five years, also discounting his debut. Whichever of those ten one wants to label Fincher's "worst" according to their own taste, be it
The Game, Panic Room, The Curious Case of Benjamin Button, Mank or any of them that don't float your boat, I would ecstatically watch that Fincher movie on a loop for three days before being forced to watch
Titanic, Avatar, or
The Abyss again.

I think you didn't get my point man. Anyways, I'll explain my point of view;
Fincher is a better director due to being more talented in visual storytelling, but since he had
Alien 3: studio interference and problems behind production, it was kinda lackluster compared to his standards.
Panic Room: this is an ok movie but far, far weaker than Fight Club mostly because it was like "Insomnia" a movie that the production wanted him to do.
And Mank: I personally enjoy The Game and Benjamin Button, no complains about them. But Mank (id put it above Avatar) was just good, and the third act disappointed me.
Piranha isn’t listed in AFI and sight and sound profile and he left before the film ended so I am not counting that, but if I did I would give the edge to Fincher because that movie was lackluster.
I don’t think quantity is important, I mean Malick directed 5 movies in 38 years right? And then went and did 3 lackluster movies that were poorly received, I doubt anyone expected that.
Here's my ratings
T2 *****
Aliens ****
T1 *** 1/2
True Lies *** 1/2
Titanic *** 1/2
The Abyss ***
Avatar ** 1/2
Se7en *****
The Social Network ****
Gone Girl *** 1/2
Zodiac *** 1/2
The Game *** 1/2
Millennium *** 1/2
Fight Club *** 1\2
Benjamin Button ***
Mank ***
Alien 2 **
Panic Room **
As I said, by an hair..
You can probably put Fincher up against any other director today, so putting him up against Cameron is almost unfair. Cameron's more of a technocrat than a filmmaker sometimes, using a feint at narrative as an excuse to advance industry tech.
The only question I'd have to think about is how I'd compare the best stuff Cameron has ever done with some of Fincher's lesser works.
T2, Aliens and T1 seems atleast comparable to some of Fincher's great stuff I guess. Especially T2..
I think Fincher is one of the best directors working today, besides Marty and Spielberg he’s my favorite alongside Nolan, but do you think a comparison between him and Coppola, Hitchcock and Kurosawa would be fair? As much as I love Fincher, I would still put Coppola above him.