A few rules.
1. No Dead Guys. No Kubrick, No Hitchcock, No Kurosawa, No Renoir, etc.
2. The list should be composed of directors whose first major films released in the 90s or later, so nobody who was making movies in the 70s or 80s either. So, no Lynch, no Gilliam, no scorcese, no Spielberg.
3. Despite rule number 2, you may include directors who released a few minor films or shorts in the 80s, but whose main body of work is in the 90s, such as Peter Jackson or Joel Coen.
Here's a list to jog your memory
Joel Coen- Fargo, Miller's Crossing, Oh Brother Where Art Thou
Wes Anderson- Rushmore, The Royal Tenanbaums
Jean-Pierre Jeunet- Amelie, The City of Lost Children, Delicatessen
Richard Linklater- Before Sunrise, Before Sunset
Darren Aranofsky- Pi, Requiem For A Dream
Fernando Meirelles- City of God
P.T. Anderson- Boogie Nights, Punch Drunk Love, Magnolia
Spike Jonze- Being John Malkovich, Adaptation
Alejandro Gonzalez Inarritu- Amores Perros, 21 Grams
Yimou Zhang- Hero, Raise the Read Latern, To Live, The Road Home
Ang Lee- Eat, Drink, Man, Woman; Crouching Tiger Hidden Dragon, The Ice Storm
Quentin Tarantino- Pulp Fiction, Reservoir Dogs
Wong Kar Wai- In the Mood For Love, Chungking Express
Tim Burton- Ed Wood, Edward Scissorhands, Big Fish
Alejandro Amenabar- The Sea Inside, Open Your Eyes
Baz Luhrmann- Moulin Rouge, Strictly Ballroom
Peter Jackson- Lord of the Rings, Heavenly Creatures
Sofia Coppola- The Virgin Suicides, Lost in Translation
Steven Soderbergh- Traffic, Sex, Lies and Videotape
David Fincher- Se7en, Fight Club
Todd Solondz- Happiness
Christopher Nolan- Momento
Lars Von Trier- Dancer in the Dark, Breaking the Waves
Cameron Crowe- Say Anything, Almost Famous
Takeshi Kitano- Hana-bi, Zatoichi
Richard Kelly- Donnie Darko
Todd Haynes- Far From Heaven, Velvet Goldmine
Michael Moore- Bowling for Columbine, Roger and Me
Sam Mendes- American Beauty, The Road To Perdition
Guy Richie- Lock, Stock and Two Smoking Barrels, Snatch
Pedro Almodóvar- All About My Mother, Talk To Her, Bad Education
Alexander Payne- Sideways, Election, About Schmidt
Frank Darabont- The Shawshank Redemption, The Green Mile
... Did I miss anyone?
My top 5.
Wong Kar Wai
Joel Coen
Quentin Tarantino (I'm over him, but he's still the most influential director in the past 15 years)
Alexander Payne
Cameron Crowe- Yeah.. he's not as good as the others as a director, but I love his movies usually.