Obviously, Psycho (1960). Gus Van Sant's semi-formidable talents aside, I'm going out on a limb and recommending the original. Black and white, Tony Perkins, and Hitchcock, Hitchcock, Hitchcock. Copy the master? I don't think so.
The Conversation (1974). The masterful opening scene of Francis Ford Coppola's other great movie is knowingly mimicked in the current Will Smith-fest, Enemy of the State, which features Gene Hackman in a semi-reprise of his decades-old turn. Once again, the tape is better, and cheaper.
The Shop Around the Corner (1940). Why wait at the end of the driveway for You've Got Mail? I know people like that Tom Hanks fellow, but I know Tom Hanks, and he's no Jimmy Stewart.
From the Hollywood Hills to Capitol Hill, everything old is new again. It fills the papers, keeps the politicians busy and even makes for good daytime TV. But you've seen it all before, fellow potatoes. And it was better the way you remember it.