In Central/South America? Africa? Asia? of course opinions will vary, but what are the generally considered best?
In Africa, I've only been to UWEC (Uganda Wildlife Education Center) in Entebbe several years ago but was quite impressed. I think it could make the Top 5, and definitely is #1 in East Africa. I've heard Mysore, Delhi and Nandankanan as the top 3 in South Asia. Of course, zoos in East and Southeast Asia will beat these. Singapore Zoo (or WRS in general) should be in the top 5 for Asia.