I thought I would be able to participate bit I just haven't been to enough zoos myself and just don't have an opinion on what would be at least two thirds of my list.Sadly the rankings have stalled. I'll complile the rankings made and formulate the composite rankings shortly, but with the ability to add potential future rankings.
Sorry I'm late to the party, here is my list!:
1. San Diego Zoo
2. San Diego Zoo's Safari Park
3. Bronx Zoo
4. Disney's Animal Kingdom
5. Toronto Zoo
6. Zoo Miami
7. Columbus Zoo
8. Minnesota Zoo
9. Henry Doorly Zoo
10. Busch Gardens Tampa
11. St. Louis Zoo
12. Brookfield Zoo
13. Jacksonville Zoo
14. Woodland Park Zoo
15. Denver Zoo
16. Dallas Zoo
17. Cincinnati Zoo
18. National Zoo
19. Tampa's Lowry Park Zoo
20. Fort Worth Zoo
21. Calgary Zoo
22. Los Angeles Zoo
23. Detroit Zoo
24. Indianapolis Zoo
25. Kansas City Zoo
I have visited all of those on my list.
My rankings:
1. Omaha’s Henry Doorly Zoo
2. Bronx Zoo
3. Saint Louis Zoo
4. San Diego Zoo
5. Columbus Zoo
6. Minnesota Zoo
7. Toronto Zoo
8. Sedgwick County Zoo
9. Woodland Park Zoo
10. Zoo Miami
11. San Diego Zoo Safari Park
12. Brookfield Zoo
13. Dallas Zoo
14. Denver Zoo
15. Fort Worth Zoo
16. National Zoo
17. Detroit Zoo
18. Disney’s Animal Kingdom
19. Cincinnati Zoo
20. Cleveland Zoo
21. Los Angeles Zoo
22. Oregon Zoo
23. Kansas City Zoo
24. Indianapolis Zoo
25. Philadelphia Zoo
I didn't include zoos I have not visited, I suspect there are several that would rank higher than the last ones on my list, but I was not comfortable guessing. Some likely candidates I have not visited are Sedgwick County, Oklahoma City, and North Carolina.
I ranked Omaha ahead of San Diego and Bronx because aside from a few exhibits that will be gone in a few years all of the habitats are really good, they have the best indoor rainforest, a huge African exhibit, a large aquarium, and an Asian highlands exhibit that is sure to be great.