I'm not gonna get into anything as vague as whether Kubrick's films, or even film in general can be called "the highest form of art", but he is IMHO the greatest director yet. Though Bergman's pretty amazing too. My faves are 1. Full Metal Jacket, 2. 2001, and 3. Eyes Wide Shut.
Comparing him, or anyone to Da Vinci is going way overboard. Well, maybe Ben Franklin... naw, I just can't think of anyone. A Renaissance man needs a renaissance.