Putting aside the acknowledged facetiousness...
The biggest difference is that most of the process in creating the Mona Lisa was done in Da Vinci's studio, considerably prior to it ever having a public viewing. The Cameron/Titanic equivalency would involve creating the sets, producing all the...
The basic problem here, as I see it, is that unless you're looking at an actual film print projected in a theater, you aren't seeing the film as it was originally intended. No matter what tools are available and no matter the skill levels of the craftsmen producing a home video presentation...