Eli Roth:
Eli Roth spent his parents' retirement money in order to produce his 2002 debut film Cabin Fever. It was a fun, creepy, and above all gory debut that put him on the map and got him recognized by a lot of people including Quentin Tarantino and Peter Jackson. After the success of his first movie, his sophomore film Hostel was highly anticipated. It was released in 2005 with solid reviews from critics and fans alike. He also made a sequel in 2007, Hostel Part II, which was another hit in the horror community. He hasn't directed a movie since, but he's produced many, and even acted in a few. There are rumors that his next directorial project will be a cannibal movie in the vein of Cannibal Holocaust.
Rob Zombie:
With his music showing much love to the horror genre, Zombie making a horror flick of his own seemed only right. In 2003 he released his hallucinatory debut House of 1000 Corpses. It was bizarre, trippy, and gory as hell. It has since become a cult hit. His second flick, The Devil's Rejects, a loose sequel to House, was met with very positive reviews and is still considered to be his best movie. After proving that he had some serious talent behind the camera, he went on to tackle the remake of Halloween in 2007. It was met with mixed reviews, but was box office hit. In 2009, he made the sequel, Halloween 2 with the same results. His most recent film, The Lords of Salem is currently making the rounds at festivals, and has been picked up by Anchor Bay for distribution.
Neil Marshall:

James Wan:
Back in 2004, a little film called Saw was released. It essentially created the "torture porn" sub genre and changed the way we saw horror films. James Wan finished this film in 18 days on a shoestring budget, making it one of the most successful independent horror movies ever made. He has since directed Dead Silence and Death Sentence (both released in 2007), and Insidious released in 2011. His next work is highly anticipated.
Greg McLean:
Australian born director showed off extreme talent when his debut Wolf Creek was released in 2005. It was his personal answer to Saw and Hostel and it was met with huge success. His second feature film Rogue, about a killer crocodile, was released in 2007 with very positive reviews. He hasn't directed a film since, but a sequel to Wolf Creek is reportedly in the works.
Adam Green:
Better late then never, Adam Green released Hatchet, a throwback to old school American slashers, in 2006. It was met with praise from critics and fans alike. He later directed some smaller films like Spiral in 2007, before making Frozen in 2010. Frozen proved he not only knew how to orchestrate mindless violence and gore, but also suspense and true scares. Hatchet 2 was released in 2010 as well but it came with so-so reviews. He also directed a segment in the sleazy anthology Chillerama, which was released in 2011. He is currently acting as writer and producer of a third Hatchet film.
Alexandre Aja:
French filmmaker Alexandre Aja burst into the horror scene with his gloriously gory debut High Tension in 2003. This gained him some recognition, and he came to the states for his next feature, The Hills Have Eyes, which was released in 2006. This gave him a name in the US as a horror master. He stumbled a bit with 2008's Mirrors, as it was a critical and financial bust. But, he was back to form with 2010's Piranha. He has been writing and producing since, and plans to direct another film soon.
As horror fans, we owe these guys our lives. They saved our genre from the dreadful 90's and reminded us how amazing good ol' bloody horror films can be. If you haven't seen any of these films, I say definitely check them out. They're all an extremely important part of the horror genre. Long live The Splat Pack!