One very talented individual has made some Doom figures, and even entire scenes, in Lego.
Iain Heath, or 'Ochre_Jelly' is the creator of the exquisitely-detailed Doom Lego sets below. He's so good, he displays his work at various conventions. My favourite is the one where the protagonist faces-off against the monster.
Check out Ochre_Jelly's Flickr page for various other pop culture phenomena made in Lego.