Actually, there are 2 clearly different methods for determining which is the "best" zoo. The method I use, subconsiously, is to look at the overall zoo -- its strengths and weaknesses, then categorize the different zoos and rank them according to their strengths and weaknesses in the different categories. In the end, I (again subconsiously) accumulate all of the ratings and sort of "average" them, coming up with an overall score for each zoo. This way, a zoo like San Diego can have a few negative rankings (ie, bad exhibits) and still be an easy #1, if it has enough positive rankings (ie, best collection, many great exhibits, key animals, etc.) to "cancel out" the few negative rankings.
The other way of determination, which apparently some of you use, is what I call the "Weakest Link" method (named after an old British game show). In this method, you simply look at the zoo's weakest points and whichever zoo has the "best weak points", that zoo is #1. This is the ONLY way that San Diego could be ranked anywhere less than the best zoo in America, in my humble opinion.
"You ARE the weakest link! Good-bye!"
Iv'e always thought you to be one to advocate one's opinion? I personally think Bronx is the best (and yes I've been to Bronx and San Diego (San Diego 3 times) so im pretty familiar with it although I haven't been since the opening of Elephant Odyssey.
The reason I think the Bronx Zoo is the best is because of the spectacular exhibitry. Congo Gorilla Forest alone is worth the admission and then some and I spent nearly an hour in that section of the zoo watching the gorillas and exploring the other exhibits. Simply seeing 20+ gorillas in an ultra-natural environment with superb viewing opportunities makes for an unparalleled zoo experience. Besides Congo there are many other fantastic exhibits that our among the best of their kind. The underrated Tiger Mountain (I didn't realize how great it was until I visited), JungleWorld, Madagascar, Asian Monorail, Baboon Reserve, and Himalayan Highlands are fantastic. I love the park like setting and how a visit to the Bronx Zoo is different each season and in my opinion zoos are one of the most fantastic places to enjoy the change of seasons! Something one cannot do in San Diego. You won't be seeing Tigers or Snow Leopards playing in fresh blankets of snow in San Diego. And there is nothing like walking around a zoo on a crisp fall day when one practically has the zoo to themselves. I also think there is no other zoo with as much a conservation initiative as the Bronx, something I find very important for a facility that is going to display animals.
And I'm not saying your wrong in saying San Diego is best as probably many more people agree San Diego is better than Bronx, but in my opinion I think Bronx is better for the reasons listed. Just trying to show a different perspective and how I think that you cannot state it as fact that San Diego is THE best when people disagree.