I list the Hughes brothers not so much for their most recent output (though I know that both The Book of Eli and From Hell have their fans), but for their first films Menace II Society and Dead Presidents. The Hughes brothers are great stylists and when the screenplay is strong, the results are compelling, and even when the screenplay isn't up to par the films are always interesting on a visual level.
The Wachowskis can, admittedly, be hit and miss. There are the highs of Bound, The Matrix, and (in my opinion, at least) Cloud Atlas, and there are the lows of The Matrix Reloded, The Matrix Revolutions, and Speed Racer. The pair definitely have vision, but that vision doesn't always translate into cohesive stories. Still their best movies are so good that their reputation shouldn't be diminished by the lesser works.
Filmmakers Albert and David Maysles are two of the most important and influential documentary directors of all time. The best known of their more than 30 films are Grey Gardens, Gimme Shelter, and Salesman, and the pair are key filmmakers in the style of Direct Cinema, with Albert is particular being noted for pioneering certain filming techniques and having been dubbed "the best American cameraman" by Jean-Luc Godard.
The inclusion of the Coen brothers on a list such as this surely doesn't even need justification. Collectively they are two of the most celebrated filmmakers working today, as adept at making deeply silly films as incredibly challenging ones, and they are arguably two of the most important American filmmakers of all time.
Juuuuust edging out the Coen brothers are Belgium's Dardenne brothers, perennial Cannes film festival participants who have twice won the Palme d'Or (for Rosetta and L'Enfant), the pair are critical darlings whose films have never earned a Metascore lower than 76 (and that's an outlier). They can't boast the Academy Awards recognition that the Coens have had, but they certainly aren't hurting for awards and nominations from other associations around the globe.