Neo-grotesk does not actually refer to style. The term neo-grotesk was invented to aggrandize the use of Helvetica, Univers, and Folio by certain designers working in the Swiss international style. The stylistic features—mechanical refinement and and horizontal terminals—that some claim differentiate the genre from its predecessors can all be found in older typefaces.

Monotype Grotesque is proto-neo-grotesk.
Arial is retro-grotesk.
Mine:
Figgins is proto-grotesk
Preface is post-grotesk.
Brown is ur-grotesk.

That pretty much sums it up.
I'm sorry to say so, Gentlemen, but sometimes it's just that simple.

Oks! Thanks!

James: that's an interesting point. Could you give some examples of older typefaces that exhibit the stlistic features you mention?

Look through this thread:
http://typophile.com/node/55329

Just flip through pages 700–765 of the 1912 American Specimen Book of Type Styles.

thanks both.