How Green Was My Valley is a virtually plotless, episodic drama about a young boy (Roddy McDowall) growing up in a Welsh mining town. It's poignant: movingly sad but not in a depressing way, portraying the human condition as a paradox of hope in the face of utter hopelessness.
If you're in the mood for entertainment, I'd opt for All About Eve, but if you'd like to be moved by a film, rent the latter. And keep the tissues handy.