Zoos - Mixed feelings

We took our 5-year-old grand-daughter to the local zoo a couple of days ago, and it rained. It was OK for the flamingo, of course, because he was in a shelter.
Any zoo is a wonderful mine of information, source of knowledge and entertainer of children.
During two hours of scattered 5-minute downpours we saw birds a-plenty, mongooses (mongeese?), lots of apes, a black bear, tiger and a couple of sea lions. It was good that we saw kangaroos, wallabies, emus and a wombat - all of which prove that even the animals are a bit different in Oz.
It's good that the zoo people in Adelaide have been able to provide roomy "real life-like" settings for most of their bigger exhibits, and the general setting there is vastly better than when I visited as child.
But the bear, while we were there, trod a constant, well-worn path into his den and back to one point a few metres out. Not much fun for him.
The tiger, in a spacious setting of realistic "jungle", paced steadfastly up and back along the back fence.
Then there were the two sea lions, swimming interminable circuits of a circular pool that looked about half a metre deep and about 10 metres across - This for animals built to range widely, designed for speed and agility.
Now, I might have the wrong idea. It could be that these big animals were not stressed, or bored, or at all unhappy. It could have been near feeding time, with them demonstrating the stress we all tend to show when we "just can't wait" for a good feed.
I know that good zoos (and ours is one) are considered vital for the preservation of many species, as well as good at entertaining and educating we humans. I know that great efforts are made to keep the animals fit and happy.
But I can't help wondering how we'd feel if kidnapped by an interplanetary visitor and exhibited in his zoo.