How about theatrical cuts vs director's cut of Cameron's movies?
To be honest I watched the DC of Aliens some months ago and I didn't like it
that much. That backstory was interesting...but eh the movie is slowed down too much. I prefer the tighter pacing of the theatrical cut. More is sometimes just...more. I also prefer the theatrical cut of T2. Don't care for the Sarah's dream AT ALL, or arnold's smiling scene. I haven't seen the TC of The Abyss in forever, so I can't say much about that, but from what I've read this is the one JC movie in which the DC changes the movie signficantly.
James Cameron is definitely not Ridley Scott.

"Fortunately" in the case of Avatar you can tell a bunch of stuff has been chopped up, so a DC should almost assuredly be superior.
As for more my JC rankings, this is it for me:
T2 (at this point it may just be the nostalgia, but I doubt it will ever be topped as the best action movie ever for me)
Aliens
AVATAR
Terminator
The Abyss
True Lies
.
.
.
Titanic
edit: HEH at all of JC's movies starting with either A or T...that's kinda weird.