Here's a brief summary of each film from IMDb:
All That Heaven Allows (1955): An upper-class widow falls in love with a much younger, down-to-earth nurseryman, much to the disapproval of her children and criticism of her country club peers.
Ali: Fear Eats the Soul (1974): A lonely widow meets a much younger Arab worker in a bar during a rainstorm. They fall in love, to their own surprise-and to the outright shock of their families, colleagues, and drinking buddies.
Far From Heaven (2002): In 1950s Connecticut, a housewife faces a marital crisis and mounting racial tensions in the outside world.
All That Heaven Allows focused on socio-economic status and an older woman younger man relationship. I loved how the main character Carrie's detached/clinical social worker daughter couldn't handle the situation. Her WASP son wasn't any better. Ron, the love interest was a novelty to Carrie at first (a nice set of muscles, as her son said), and she was willing to let him go to keep her children's approval (and maybe that precious social status, too). But love conquered that in the end and they became equals who'd live a non-snobbish lifestyle. The doctor character was a voice of reason and support for Carrie, so that was refreshing.