I was thinking about this and to me it boils down to three, but its tough to choose between them: a.) James Cameron: Terminator 2, True Lies, Titanic. Terminator 2 really started the CG era and I think that film might be the biggest turning point in the modern blockbuster era since the original Star Wars (1977). True Lies was a hit, albiet not exactly a masterpiece. Titanic was the biggest grossing film of the 90s and no.1 all-time without accounting for inflation. A true international phenomenon. b.) Steven Spielberg: Jurassic Park, Schindler's List, Saving Private Ryan, Hook, The Lost World, and Amistad... Mr. Spielberg was very busy in the 90s. Jurassic Park took CGI to the next level and was a monster hit, while Schindler's List rang up the Oscars. Saving Private Ryan was hailed for its realism. While I like both Hook and Amistad, I know those film's have their detractors. The Lost World was a bit of a dissapointment, but still has some brilliant sequences. c.) Quentin Tarantino: Resevior Dogs, Pulp Fiction, Jackie Brown. Also penned Natural Born Killers and From Dusk 'Till Dawn. Certainly brought forth a style that's been copied and imitated to death by now. No denying the impact. Jackie Brown maybe wasn't the same home run his previous two films were, but it was still a solid (perhaps a bit more mature) piece of filmmaking. I get the feeling his films will be closely identified and associated with the 1990s and the violent popular culture that infused movies, television, and music at the time. I don't know who I'd vote for. I'm leaning more towards Cameron since T2 really I think opened a lot of doors that other filmmakers like Spielberg, Lucas, and Peter Jackson (who I might add, should be the current favorite for this decade's top director) utilized as well. And while its become a popular film to knock on these days, there's really no denying that Titanic was an incredible phenomenon.