If the point of a thread like this is to inspire debate - and I think it is - here’s a comment which merits such debate!
San Diego may not be perfect, but, really - having visited nearly 400 zoos worldwide, including most of the renowned US collections, I would put it so far ahead of the rest as to make any “match” absolutely one sided. For me, all it lacks is a (physical) sense of its history - if it had a 1927 zebra house now converted into an armadillo exhibit, or an erstwhile aquarium in which could now be found a top notch restaurant, it really might be perfect. And even there, despite the absence of many charismatic old buildings, there is an eye on the past, through publications and signs and memorials, which puts others to shame....