All the preparation in the world!
Alfred Hitchcock's thing was planning. Scheming. Preparing. His job was to take a scenario, coax it through a writer into a script, and then figure out the geometry of the thing. Camera angles, lens lengths, the shapes and colors of the foreground and background. He took notes, he storyboarded, he imagined and decided and determined and produced. By the time the first frame was shot, he was essentially finished. He had produced a specific plan, and filming was just the tedious process of capturing all the little snips of colored thread so that they could be sewn into a suspenseful needlepoint later on. He didn't shoot coverage, he didn't run a dozen cameras so he could make up his mind later, he didn't waste film on anything; he just shot the plan. This way, if he was fired before the edit was done, the movie would still look like he planned, because there would be no alternate footage or angles to choose from. Actors - props that eat - were expected to know their roles, literally and figuratively, and do their best not to mess it up. (I don't think Hitchcock would go in for the creepy Zemeckis-favored animation thing though, that's giving whole staffs and departments worth of people the chance to screw up the performance.)
In theory, if you had all of Hitch's notes and storyboards and perhaps, in the spirit of planning, you discussed his intentions with him, he wouldn't even have to show up. Someone else could relay the same set of decisions, made in advance, follow the boards, shoot the plan.
So how did Gus Van Sant screw up Psycho? I'll admit, I haven't seen his remake since it was in theaters. It might be better than I remember it, what with all the laser pointers and people yelling, bur probably not by much. They not only had the original materials, they had the original film to look at! But maybe that's the trouble. Maybe too much effort was spent on imitating the original cast instead of acting. Maybe it was mis-cast. Maybe part of the problem was that it was shot in color - Hitchcock certainly could have shot it in color, and had already done several color films; the black and white was a choice.
So....what? Imitation is flattering, but lousy art? There was more method to Hitchcock's madness than met the eye? Does the meaning of the film change when the audience goes in knowing the surprises on which the original was hinged? Was the movie actually okay, just not able to stand its own weight, in the form of the original's legacy and the criticism that comes with touching it?
On a somewhat related note, did anyone actually see that Twilight movie? There's a mountain of press on the subject of how popular and oft-mentioned by the press it is, but I haven't seen anyone discuss whether or not it's any good. (although rotten tomatoes suggests it's twice as good as Punisher: War Zone, or half as good as Bolt.)