As I have said before....
Some road-side crap hole, ya shut the thing down. But the majority of the zoos in the day and age are far from the concrete and steel they used to be and anything but cruel.
The plus side of zoos greatly out shadows the negative and that is why they (most of them) should not be shut down.
Yes the animals might be stuck in captivity but through them they serve as ambadassors for their wild brothers and sisters. It gives the public a chance to connect and learn about things they would have never had the chance to before.
Zoos have also transformed greatly over the years. They are changing from the old concrete and steel pits/cages of the past to wide lush open habitats with live plants, waterfalls, etc. On top of changing the way they house animals they have also changed how they run things. Though zoos are still out to make money (to keep doors open since most are non-profit) they have and still are moving to more of a conservation and education outlook rather than strictly entertainment. Plus they bring in a HUGE amount of money for the local economy. More people go to Zoos in the US than go to all the professional sporting events combined each year.... that adds up to a ton of money for the city each zoo is in... be it a local hotel or some small mom and pop shop people stop by on their way to the zoo.
On top of all that, zoos work a great deal in rescue projects with injured wildlife as well as breed and release programs with endangered species. For example sea world and other facilities in FL were being over-run with injured manatees to the point that they had no more room to house them. To help a handful of other zoos built exhibits where the injured/sick manatees could recover before they were released. With breeding there are many zoos who work together with the US govt as well as programs around the world to breed endangered species and release those that are born back out into the wild to help with new healthy blood lines. The California Condor would be extinct today if it was not for such programs.
Zoos also use the animals in their collection to help learn how to better care for those that are in the wild. Back to the manatee example. There is currently a virus floating through the wild manatee popluation that the science world has yet to figure out how it happened and how to stop it from spreading. Zoos are using their captive manatees with the virus to try and find a treatment or cure so that they can help the wild populations and re-release those that were sick.
So do I think animals should be kept in zoos? In this day and age it is a 100% yes. Do I think that zoos are cruel? Some yes, but the vast majority have changed and have become wonderful places.
Because of what man has done to this world it is something that is needed. However, it should only be done for the right reasons and under the right conditions... that is what makes it not cruel.