Joel & Ethan Coen
This team of brothers have been Co-Producing & Co-Directing many great films since the 80's, but most notable of the 21st century are probably O Brother, Where Art Thou?, 2000, No Country for Old Men, 2007, Inside Llewyn Davis, 2013 & Hail, Caesar!, 2016. They also Executive Produce the series Fargo, & maybe worth mentioning, Executive Produced the original Bad Santa, 2003. Each of the two have about 23/24 Directing & Producing credits.
Coming a long way from Troma Studios in New York, James Gunn is a Writer / Director who's delivered a few good cult comedies along his path to helming Marvels break out hits, Guardians of the Galaxy, Vol. 1 & 2. He's an accomplished Writer with TV, Gaming & Film credits who's also Producing / Directing & Executive Producing some major upcoming projects.
With 15 Directing & 16 producing credits, Alejandro González Iñárritu has been quite busy since his first big hits Amores Perros, in 2000 & 21 Grams in 2003. Recently he's won a number of Academy Awards for Birdman, 2014, & The Revenant, 2015.
Martin Scorsese
With 58 Director credits & 58 Producer credits over all, Martin Scorsese is a masterful filmmaker who's still Directing hits in the 21st century. Most notable being Gangs of New York, 2002, The Aviator, 2004, The Departed, 2006, Wolf of Wall Street, 2013 & Silence, 2016. Let's not forget he's also Produced the 2 major HBO series Boardwalk Empire & Vinyl. He's also been involved in Producing a number of Documentaries in the past decade, most notable Before the Flood, 2016.
Alfonso Cuaron
Since Y tu Mama Tambien in 2001, Alfonso Cauron has released a number of critically acclaimed films. In 2004 he brought us Harry Potter & the Prisoner of Azkaban. In 2006 he impressed with the highly acclaimed Children of Men. A sophisticated Sci-fi with a strong human element. More recently Gravity, 2013, won a number of Academy Awards for its complex visual sequences, & technically innovative cinematography.
Neil Bloomkamp
'District 9' may be one of the funniest, most poignant & masterful films ever produced. Its a rare gem that transcends an epic spectrum ranging from brutal & hilarious absurdity to comically horrific tragedy, & finally spits the audience out at a point of love and compassion. Its complex. Its writing, acting, construction & execution are absolutely brilliant, & I haven't even gotten to the VFX yet. The VFX are amazing as well.
Elysium & Chappie don't quite par, lacking the depth & arch of 'District 9', but they are still great Sci-Fi flicks that are fun to watch & visually stunning, with a degree of realism that only Bloomkamp seems able to deliver.