A " Sleeper hit " is ( in movie terms , something I know about ) is a hit movie that no one expected to be a hit. It is a hit movie that comes out of nowhere. A good example is " The Blair Witch Project " it was a movie no one heard about but it blew it big time from nowhere. A little movie that made over $100 million dollars.
A cult hit is a movie which isn't really popular but has a following. A great example ( AND A GREAT Movie ) is NEAR DARK ... which is the best vampire horror movie you have probably never heard of. I highly recommend it. IT didn't break box office records, I doubt it made it's money back but it has a HUGE cult following and people constantly recommending it. Another cult hit which is BETTER than both Matrix sequels is EQUILLIBRIUM ....... the best Matrix sequel that isn't.