Visconti's first. I'm not a big fan of Italian neo-realist cinema, but it's clear that Obsession was a key film in its rise, even when the real boom would only come in the next decade. All the trademark elements are already here and it's a big change from the kind of cinema that was popular at the time.
My biggest problem with the movement is the excessive/expressive acting, which stands in strong contrast with the realist overtones of the story and the cinematography. There are too many grand gestures, too many overt emotions, almost as if the actors were still used to doing silents. It takes me out of the drama and makes for rather annoying characters.
And that's a real problem, because Visconti leans quite heavily on the drama. The story is pretty basic, the crime elements are minimal and the pacing is slow. The cinematography is unremarkable, the soundtrack rather shrill, so aesthetically there's not much there either. Not my thing, but no doubt an important film.