I realize this is an odd question. Every film made by Quentin Tarantino is great, or at least close to it. Scorsese always seems to direct great films as well. I give more credit to Tarantino for writing most of the movies he's directed. What is it that certain Directors do that can make a film great?

Talent?

They don’t insult the intelligence of their audience.

Scientology?

I think "taste" is important too.

An unrelenting faith in oneself.

Most filmmakers are hit and miss. (Francis Ford Coppola made Jack for chrissakes!) There's also a certain snobbery that goes with the belief that one director is a genius who puts out nothing but gold and another is a hack who puts out nothing but garbage. The best example of this is John Waters and Kevin Smith. There are people will argue that Pink Flamingos is a work of subversive genius while Clerks is a third rate student-level film. People can push and shove on that, but it's all subjective. In reality Waters and Smith view each other as contemporaries.

I can't think of single filmmaker that I admire that hasn't put out a dud in their career. And then there are filmmakers who was scorching hot in their heyday and then kind of fizzled out (hello, Oliver Stone!). And there are filmmakers who made one film that I love (like Paul Greengrass's United 93) and I could give a crap about the rest of their filmography. I don't care, I just focus on the movies first and who made them second.

Steven Spielberg comes to mind. I would say he's honed his craft after a very long career and he's always been about entertainment. When he's made more serious movies he's always made them thought provoking.

Quentin Tarantino, Edgar Wright and Sergio Leone. No duds for me.

Many of them go by the 'good enough' moniker for their movies. Someone like James Cameron puts his heart and soul in every movie he does, as it's almost personal to him. Then a guy like JJ Abrams (who reboots many popular franchises) churns them out like they are an assembly line. Abrams is happy with movie that is 'good enough' for the masses, where Cameron is obsessed with the movie being great. Both are successful at what they do and make alot of money for the studios, but only Cameron's films hold up year later because he tries to make it great.

I wouldn’t say assembly line. He’s directed six films in 15 years. JJ shouldn’t get knocked solely because he makes franchise films. I’m sure on a lot of them, his hands are somewhat tied to the source material From interviews and things I’ve read I thought Super 8 was a personal project.
Compare that to Cameron who’s directed seven films in 40 years. Two of those films have basically encompassed his whole career since 1997. There’s a fine line between passion and obsession.
That being said he makes great films. I just wish he’d get his head out of his own ass and make something other than Avatar sequels.