When I realized that Sidney Lumet made two really great movies spanning FIFTY YEARS (12 Angry Men, '57, and Before the Devils Knows You're Dead, '07) I went on a binge watching many of the ones in between: Running on Empty, The Verdict, Pawnbroker, Long Day's Journey into Night, Serpico, and Find Me Guilty. There's two others I'd already seen - Dog Day Afternoon and Network.
Favorite is not a surprise: Dog Day Afternoon.
One I think is underrated is Find Me Guilty. Serpico was a little overrated.
If it was my birthday today I'd watch a couple more.