Bob,
I had the same thoughts when I saw monkeys at a zoo a while ago. I did not even take pictures because it seemed so sad.
On a second thought, I was not so sure anymore if we always interpret their facial expressions right. But I can definitely imagine that live in most of these enclosures is kind of dull for an animal of high intelligence. Not sure what makes life harder, boredom or struggle for survival.

Edit: But the picture is great