The 1960's had the hit TV show that viewers treated and still treat wrongly like some old friend. Silly on two counts:

1. It is not a personal friend it is an impersonal TV show

2. It actually had much brutality including deaths on screen

Nonetheless, this show and (for what small number of viewers saw it in theaters) the 1966 film represented public craving of the Caped Crusader.

For 21 years Batman was out mostly as a cult (outside mostly of innocent cartoons). Then in 1989 this hit film (of the actually same title as the 60's Batman film) came along and Batman the cult was revived fully. Now more dark than the 60's actually also brutal Batman. We had several sequels to it by the 90's (with different Batmans). Now think about something. Why did this very movie linger in our thoughts so much throughout the 90's? Why did it not go the way the original Poltergeist did due to its own sequels in the 80's?And now it seems like we are getting Batman films all the time. Hard to even keep count. This movie, again, brought Batman totally back (though Nicholson only played Joker once)! Those 21 years between '68 and '89 seem pretty novel now.