Channel 4 is giving both True Blood and Generation Kill their first airings on terrestrial television on Wednesday, one straight after the other.  It’s an odd juxtaposition, because apart from the fact that they are both made by the American cable company HBO, they could scarcely be more different – True Blood, a tale of vampires coming out of the closet in the Deep South, is a fantastical, at times hilarious chunk of modern gothic; Generation Kill, based on real events and people, is a painstakingly realistic seven-part depiction of life for an elite detachment of US Marines in the first phase of the Iraq War.