When you ask people "Who was the actors who made the 1970s film renaissance possible?", they usually name Jack Nicholson or Al Pacino or Robert De Niro. I prefer to say Elliott Gould instead.
Partially, people tend to say Nicholson or Pacino or De Niro because all three have remained big stars to this day. All three have generally selected good roles that kept their careers moving forward (until the point that, today, they're universally regarded as the greatest of all living actors). Gould's greatness was much more condensed into a relatively short time frame (1969-1975 or so) - by 1979, he was taking small roles in the Muppet movie series.
Why I think Gould is such a ground-breaking actor is that Gould's acting made a particular realm of male psychologies and personalities possible within the American cinema. James Dean and Marlon Brando made an initial foray into exploring the inner nature of American masculinity. However, neither was able to dig very far - partially, because neither is plausible as a loser or schmuck character - Dean and Brando were just too handsome and too obviously sexually appealing to women.
No major actor was able to, in movie after movie, build a career based upon as non-heroic characters as Gould did. Dean and Brando's characters, whatever else their flaws, were always interesting and exciting (Dean's character in
Rebel is bullied, but eventually able to win the chickie race
and get the girl - Gould's characters would have just been bullied). Gould was able to invigorate what losers or schmucks into, no, not heroes, but a sense that these characters are what real lives actually are. They don't become heroic, but become
real instead.
The height of Gould's career was extremely short, and the core of his work only a handful of movies -
Bob&Carol&Ted&Alice (1969),
MASH (1970),
Little Murders (1971),
The Long Goodbye (1973), and
California Split (1974). Of these, perhaps
California Split is my favorite. More on Gould later.