Recommend a movie from the 1970s to watch

When I read your question, The Last Detail came to mind right away.

Shampoo (1975) is one that's maybe not too obvious. It's about 70s Hollywood, with Warren Beatty playing a womanizing hairdresser. If you're interested in that kind of behind the scenes look at the entertainment industry, you might find it interesting.

Prophecy (1979)

andy warhol's bad (1977)
beyond the valley of the dolls (1970)
land of darkness and silence (1971)
house (1977)
hardcore (1979)
the devils (1971)
female trouble (1974)
walkabout (1971)
multiple maniacs (1970)
the velvet vampire (1971)
the black stallion (1979)
starcrash (1978)
andy warhol's frankenstein (1973)
alice sweet alice (1976)
race with the devil (1975)
the long goodbye (1973)
island of death (1976)
female prisoner #701: scorpion (1972)
the baby (1973)

Don't Look Now
Scenes from a Marriage
Stalker
Murmur of the Heart
Murder on the Orient Express
3 Women
The Anderson Tapes
Manhattan
Face to Face

I got two of Lee Marvin's movie here.

The Parallax View (1974) Warren Beatty. This movie is riveting, enthralling.
Emperor of the North (1973) Lee Marvin, Ernest Borgnine, and Keith Carridine.
The Big Red One (1980 - technically made in 1979) Lee Marvin, Mark Hamil, Robert Carridine. Great war movie.

70's films with man in the title tend to be good!

The Wicker Man
The Man Who Would Be King
Marathon Man
Superman

The Warriors (1979) Micheil Beck, James Remer, David Patrick Kelly.
The Wanderers (1979) Ken Wahl, Karen Allen, John Friedrich.
The Deer Hunter (1978) Robert De Niro, John Cazale, Christopher Walken.
The Conversation (1974) Gene Hackman, John Cazale, Cindy Williams.

I love the classic horror movies from the 1970s. The Exorcist and Halloween are really good films to watch....