Mixed,
there are many animals that can be housed perfectly well in captivity, and live way beyond their natural lifespans. Reptiles, amphibians fish, and many invertebrates being good examples.
many of these are also animals that could benefit the most from conservation efforts, as there may, for smaller species at least be just enough enviroment left to re-introduce them.
The problem is, the public won't generally care or more importantly pay, to see these creatures- they want the lions, tigers and elephants etc, Animals that have drawn the short straw of being contemporaries of humans.