Are we arguing that the SDZ have not kept pace in terms of design quality or their rate of renovation? They're coming up with exhibits as fast as anyone else, certainly not the fastest, but they're also bigger than most zoos and have tougher terrain. Construction also tends to work out of favor for SDZ because tourists don't expect to see a ton of construction work being done when they come.
For the average zoo visitor at SDZ, their exhibit design is over-rated, simply because the average local or tourist hasn't been to many zoos and can't compare the SDZ with what other zoos have done. I have to agree that Tiger River and the Kopje exhibit are really the zoo's only spectacular exhibits, and that their exhibit design is not very cutting edge, but I think across the board SDZ is probably the greatest in the United States. All their newer exhibits, with the exception of EO, are still good exhibits even if they are not cutting edge. Of course, this is no excuse for a zoo that can do cutting edge design, they do read as "great" exhibits to the average visitor. Plus they have all the husbandry equipment, keeper amenities, and infrastructure required of modern zoos.
Now I haven't been to any major zoos in the South, but I have been quite a few zoos that have been argued as contenders by a few on this site, such as Bronx, Omaha, St. Louis, Columbus, Oklahoma City, and Woodland Park Zoo. Across the board San Diego does trump them on other categories than exhibit design that I think the carries through to the average zoo visitor.
Entrance Area: Flamingo Lagoon is one of the best opening scenes walking into a zoo. Guests don't like to walk far between exhibits and the SDZ makes a great first impression by having an exhibit right at the entrance that looks nicely. OKC and St. Louis have great entrances too, but flamingo lagoons is better than any of their closest exhibits.
Reptile House: I would say its better than Saint Louis and Bronx's.
Guest Services: Bronx, as expected with NY, has terrible guest services. I wouldn't expect to see someone in SDZ keep a job with profane language. Zoos are family-oriented attractions and should be conducted as such. I have always had good experiences with vendors at the SDZ. I am not arguing that the SDZ has the best services, but it definitely has it taken care of.
Food Service: Although pricey, people here have mentioned that they probably have the best food and best variety. Treetops terrace and the Sabertooth Grill are great relaxing areas to eat with satisfying views. Most Zoos only have two large food areas through their zoo, SDZ has at least 5.
Collection: Still the best collection around, and we all know no average visitor cares about Borneo bearded pigs or Barbary deer. They expect to see lions, giraffes, elephants, bears, and tigers. As you start to go down the most-well known animals list, SDZ has them, with the addition of two huge favorites: Pandas and Koalas, which the SDZ has great history with both.
Location: Best climate in the United States -> best horticulture collection in a zoo, most sunny days, more outdoor exhibits. Also set in scenic Balboa Park, which practically put San Diego on the map. The Bronx Zoo is set in the Bronx, how friendly are 13 feet fences with barbed wire?
Sorry to make another large post about the San Diego Zoo; I'm pretty sure most people here think its all I talk about, but oh well. I am critical of it just as most people here, but I do because it is my home zoo and its a shame to watch it depreciate in quality. Its not the best in terms of exhibit design at all, definitely over-rated but still the greatest.