From the Comics Continuum:
Mark Steven Johnson, who brought Daredevil and Ghost Rider to the big screen, told The Continuum that his attempts to bring Garth Ennis' Preacher to HBO as a series were close but ultimately unsuccessful.
"We were budgeting and everything and it was getting really close to going," Johnson told The Continuum. "But the new head of HBO felt it was just too dark and too violent and too controversial. Which, of course, is kind of the point!
"It was a very faithful adaptation of the first few books, nearly word for word. They offered me the chance to redevelop it but I refused. I've learned my lesson on that front and I won't do it again. So I'm afraid it's dead at HBO.
So the Preacher adaptation gets shelved, and Johnson takes the opportunity to say the studios were responsible for his other comic book adaptations being shite.
My guess, based on his career output, his Preacher would have also been awful.