What's the quality that gives some lenses (like Minolta G) a "3D" look?

The Sharpness, contrast and a nice bokeh of the lens is essntial for the "3D" look. but the copositionn, background and background-light plays a big role too. So you have to "see" the 3D yourself, but your lens should be capable of creating a sharp shot with nice bokeh too.

Here is my 3D-shot of the day, fresh from today, with Tamron 70-200/2.8 (the good old cheap one). The nice bokeh of other ducky in the background plays a big role in popping out the 3D-ducky out of your monitor ;).