Pretty much what the title line said:what are the highest earning movies that were rated X and/or NC-17? Bonus points for factoring in things like inflation, theatrical release vs ancillary sales, domestic vs global box office, etc.
Box Office Mojo lists Showgirls as the top NC-17 film with $20.35M.
However, back in the days when X was used for standard releases (pre-porno), films like Midnight Cowboy and A Clockwork Orange would probably count. Those two films made $44.79M & $26.59M respectively (unadjusted for inflation).
I would have guessed Henry & June. Pleased to see it came in second. I enjoyed that movie.
Basic Instinct deseves mention because though it was edited a tiny bit to escape the NC-17 rating in the U.S., it was released uncut elsewhere and restored for the home video market. It wouldn’t surprise me if the overseas box office (not to mention the home video sales and rentals) dwarf Mojo’s entire list combined.