well technically, film can't be replicated because the image is not graphed with film in a x/y axis sense; it is photogenically matted onto a light sensitive emulsion.
But it is quite easy to make digital look exactly like film to the average viewer. Especially if you are shooting a fancy HD digital camera (Arri D20, RED, etc.) because you have more freedom for post when you shoot such formats. Things such as grain, shutter, gamma curves, color balence, contrast, etc. can all be adjusted in said process.
To contradict my statement, it may look exactly like film to a typical viewer, but waveform monitors will show that they are way off from each other even if you are successful in duplication the film-like ambience.