Dont really have a single favorite, so Ill just list a few.

Quentin Tarantino - The Hateful Eight
Wes Craven - A Nightmare On Elm Street
Sam Raimi - Evil Dead 2
John Carpenter - The Thing
Steven Spielberg - Jaws
David Fincher- Seven
Stanley Kubrick - A Clockwork Orange
Francis Ford Coppola - The Godfather
Christopher Nolan - Interstellar
Tim Burton - Ed Wood
George A Romero - Creepshow
The Coen Brothers - Fargo
Terry Gilliam - Fear & Loathing In Las Vegas(as single director. Monty Python And The Holy Grail overall)
Peter Jackson - Braindead(AKA Dead Alive)
Joe Dante - The Burbs

Several others, but thats enough for now

Spielberg: E.T.

Oh, I forgot Quentin Tarantino and Christopher Nolan.

Many great directors still have some duds (even Spielberg, Hitchcock and Cameron), but I have every Tarantino movie since Reservoir Dogs and I love them all! Can't name a favorite, most of them are perfect IMHO. If I had to pick my least favorite... Four Rooms or Death Proof, which are still very entertaining.

The same goes for Christopher Nolan. I have every of his movies since "Following" in my collection and was never disappointed. 

Ridley Scott for Alien and Alfred Hitchcock for Psycho. There are many other excellent directors and movies out there ( and both have other amazing movies as well) but these two films left an impression on me that no others did.

My favorite "mainstream" Hollywood films of the last say 40-ish years are

Terminator 2, Jurassic Park, Braveheart, Titanic, Dances with Wolves, Gladiator, Shawshank Redemption, The Matrix, Die Hard, LOTR trilogy ... yeah I'm unapologetically a lover of the big blockbusters when they are done well. Then I have a soft spot for screwball comedies like Wayne's World and The Wedding Singer. If you want to count the 70s/80s then add The Godfather I/II, Rocky I-IV, Star Wars OT, Back to the Future Part I (sorry Pt 2 and 3), Ghostbusters I (not II), Aliens, Coming To America, Close Encounters, Indiana Jones OT (1/2/3 only). 

So I suppose in that sense, James Cameron is my favorite director as he has two films on that list whereas everyone tops off at 1. Spielberg would be close I guess, Catch Me if You Can is a film I enjoy so that with Jurassic Park would tie him with Cameron, but I like True Lies too, so T2 + Titanic + True Lies has that beat.

I hate to say it but I hate the cinematographer Steven Spielberg has worked with post 1993 ... I don't like the look of any of his films since then really. Much prefer 70s/80s Spielberg.

Not the best, but I have a soft spot for Paul Verhoeven. Never boring, often provocative. My faves in order:

1) Starschip Troopers
2) Zwartboek (Dutch movie)
3) Basic Instinct
4) Robocob
5) Total Recall
6) Turks Fruit (Dutch movie)
7) Showgirls

Not a favourite, more of a Tier. A mostly standard list, though some of my picks are atypical for the director (I'd guess 98% of Wilder fans would say Sunset Boulevard, also one of my favourite films).

Hitchock → Vertigo
Wilder → The Apartment
Kon → Millenium Actress
Miyazaki → Princess Mononoke
Eggers → The Witch
Aster → Hereditary
Verhoeven → RoboCop
De Palma → Scarface
Kubrick → 2001
Cameron → Titanic
Ridley → Blade Runner
Scorsese → Goodfellas
Mann → Collateral
Romero → Dawn of the Dead
Antonioni → Blowup
Fellini → 8 1/2

Updated from ideas from other posts:
Carpenter → The Thing
FF Copolla → Dracula
Nolan → Interstellar
S Copolla → Marie Antoinette
Anderson → Grand Budapest Hotel
Coen Brothers → The Big Lebowski

IMO, he only ever did one really bad film, and it wasn't his fault: Hollow Man.

I also really like Flesh + Blood a lot. It kind of has a Kubrick on crack vibe in the way Basic Instinct kind of has a Hitchcock on crack vibe.

Awesome! Another Hateful Eight fan, a lot of people didn't like that one. But it is by far my favourite from him.
Also love Evil Dead 2, The Thing, A Clockwork Orange, The Godfather, Interstellar, Fargo, I have to update my list!

Aha did not know this one. So I just looked up a trailer on Youtube. It got Rutger Hauer in it. THAT peaks my interest. Thanks for the pointing this one out.