The first one was at least kinda shocking, and probably was even more-so for the 60s crowd. I remember watching it with my dad, who had seemingly forgotten all about the ending. But the cinematography was cool and it more-or-less introduced Jack Nicholson to the mainstream and had a pretty rocking soundtrack. Compared to other zeitgeisty movies about a certain movement or ideology, it's one of the few I can think of that ends in unexpected tragedy. The rest, you see it coming from a mile away.
From the moment our main character (played by Phil Pitzer, a lawyer by profession who sunk his cash to make what amounts to his self-insert Easy Rider fanfiction) says, "The Sky was crystal clear, just like 9/11" it's all just one big train wreck.