Have you seen the dropbear exhibit?
The best zoo I’ve visited is the Toronto Metrozoo.
I can’t believe the OP mentioned my hometown zoo! I’ve been to San Diego, which is awesome, but Riverbanks here in Columbia is still my favorite. Feels like home.
I’ve always really enjoyed the Baltimore Zoo, the National Zoo in D.C. and the National Aquarium in Baltimore.
And for a small city zoo, the Vilas Zoo here in Madison can’t be beat, IMO. Giraffes, Rhinos, Polar Bears, Lions, all kinds of Primates, Elephants - a LOT more than I expected when I walked in.
Plus, it’s free and a 5 minute bike ride from my house. 
For the large zoos I like the Bronx Zoo followed by the San Diego Zoo.
New Orleans and Cincinnati had good zoos.
The Turtle Back Zoo in New Jersey is the best small zoo I have been to.
Cape May Zoo is worth the visit.
The Baltimore Zoo was not very good and the LA Zoo is improving yearly.
The Staten Island Zoo is the worse Zoo I have been to.
Space Farms in North West NJ is a great Zoo and museum that I look forward to visiting again. I never even heard of it until last year.
It has been a while but both the Dreher Park Zoo and Loxahatchee near West Palm Beach were good zoos.
My favorite zoo’s are Omaha’s Henry Doorly zoo and the San Diego zoo.
I grew up in Omaha so I spent the first half (15 years) of my life going to the zoo multiple times per year. They kept adding to it, and good stuff too.
I went to the San Diego zoo a couple of years ago, and man, that place is freaking huge. I adored the polar bears there, they were hamming it up for the crowds.
My favorite is Henry Doorly in Omaha, too. They have many cool indoor exhibits. Haven’t been there in a few years, would like to get down there again soon.
Detroit has a tiny zoo on Belle Isle in the Detroit River.
I would go there all the time to watch the bears. They are long gone, but there’s still a few animals and a great Fish House.
I’d go you one step further and say that the San Diego Wild Animal Park is the best Zoo in the world. It’s not that San Diego Zoo is bad, og knows it’s been the model for nearly every other Zoo in the USofA, but San Diego Wild Animal Park is breaking new ground just like it did with the Zoo.
By the way, if anybody besides the OP is in the area and likes penguins, they feed them on a regular schedule and they all jump into the water and swim around. I used to love it when I was a kid. (Hell, who am I kidding. I still love it.) Also, we now have koalas and gorillas! I believe we are nationally quite well regarded; our golden lion tamarind breeding program used to be very well known, I think.
It was Riverbanks that made me fall in love with penguins. I spent an entire Sunday waiting for the feeding time. I wish I could have met with you when I was there, Zsofia.
SSG Schwartz
I’d have to say the one in Mexico City, which me and my partner saw back in 2001, for a number of reasons. It was quite up-to-date wrt the animal enclosures, especially the Great Apes exhibits – San Francisco’s gorilla enclosure equals Mexico City’s, but it’s hardly superior. Also, there was a larger and wider-ranging collection of animals there than in the Denver zoo or even the Washington DC one, to say nothing of my hometown zoo out on the Great Highway (there were even mandrill baboons in the Mexico City zoo – the only time I have ever seen these most remarkable creatures alive in the flesh, and I was thrilled to find out that yes, the males’ faces really* do * have those vivid reds and blues).And in the reptile house, there was an exhibit of rattlesnakes from all three of the Americas which just blew us both away. Especially the beautiful green and black one that was native to the jungles of the Yucatan.
I’ve never been too fond of London Zoo - the animals tended to look rather miserable, and it isn’t all that big. However if you are in the UK Longleat Safari Park and Marwell Zoo are worth a visit.
We went there a little less than a year ago. I thought it was pretty good. We went during the week when it was very crowded with a lot of school groups.
My advice is to try to get away from the main entrance, the exhibits near there were hard to enjoy because of the huge numbers of people. As we moved further away from the entrance I found myself enjoying the zoo more, maybe they keep the more interesting animals in the outlying regions of the zoo or else it was just the crowd factor.
For context of the zoos mentioned in this thread I have been to the Bronx zoo many, many times although not in about 20-25 years, I have been to the Franklin Park zoo in Boston, the Taronga zoo in Sydney and the San Francisco zoo, all of which I enjoyed. (The Franklin Park one was the least impressive, mostly due to its relatively small size compared to the others). I’ve also been to a fair number of aquariums. I admit to being something of a nature freak.
I go about 2-3 times per year to the National Zoo in DC. It is my favorite Zoo because of my decades familiarity with it though and not necessarily because the average you, zoo aficionado reading this thread, will find it a kick bottom zoo per se.
I guess some neat things are the Panda Family Momma Bear, Daddy and DC Native Baby Bear - that is fairly unique. They have a pretty cool Amazonia exhibit but beyond these two it is a regular Zoo. It’s nice, laid out by the guys who landscaped the Capitol grounds - it is ~130 years old but you don’t get that sense - with everything you’d expect at a Zoo but nothing SPECTACULAR.
Having said that the National Zoo is part of the Smithsonian and so is free and has some federal bucks that it pours into conservation and breeding around the world - so the “National Zoo” is much bigger than its footprint in DC which is kind of cool. Further, because Blacks were excluded from the White House Easter Egg Roll until the 1950’s (yeah you read that right), a +100 year old tradition has developed that on Easter Monday Black Washington goes to the National Zoo – it s a cool family oriented tradition and the Zoo has learned to embrace and celebrate this tradition.
The Baltimore Zoo is the best Zoo I have ever seen for the under 6 set. Lots and lots there for the tiniest walking-abled tikes and aimed at them.
Well, it’s actually the “Metro Toronto Zoo,” but you’re close enough. I like that one too; when my wife and I lived in the Toronto area, we had a membership to the zoo, and would visit about once a month or so. They had a number of animals that you were unlikely to see in most other zoos: komodo dragons, naked mole rats, pipa toads. And occasionally, koalas on loan from San Diego. Great zoo.
I’ll make mention of the Perth (Australia) Zoo here. True, it may not be as big or as well-known as others that have been mentioned, but what it does have, are a number of native-to-Australia animals that we’re unlikely to see in most zoos in North America. Kangaroos and koalas, of course, but also numbats, quokkas, and (of course) black swans, among many others. I’ve been to Perth a few times, and I always try to include a visit to Perth Zoo when I’m there.
If aquariums count as zoo-like, then I will say the Osaka aquarium was fantastic. The whale shark there is simply amazing.
I only brought up Zoos in my earlier post.
For aquariums and safari parks:
The National Aquarium in Baltimore is great.
The Aquarium as Epcott is great.
The New York Aquarium in Brooklyn is great. I love the Beluga Whales. (It is run by the same group as the Bronx Zoo. The Wildlife Conservation Society)
The Aquarium in Camden, NJ is okay.
The Aquarium in the Mall of America was not really worth the visit. If you are already there, sure go see it, but do not go out of your way.
In Point Pleasant NJ there is a tiny little Aquarium on the Boardwalk called Jenkinson’s. It is great for its size and price for about an hour’s enjoyment.
The Wild Safari Park at Great Adventure (Jackson, NJ) seems to go through phases. Lately is has been well worth the visit. When I was young, Lions would roam right up to the cars and occasionally sit on them. Baboons use to come by and break antennas and rip soft roofs up. Great fun as a kid in the 70s.
What Exit?
Bad news - they’re no longer there. But we do have a baby walrus, that’s very cute.
I’ve got to echo the praise for the San Diego Zoo.
Here’s one no one’s mentioned yet - the Fort Wayne Children’s Zoo in Fort Wayne, Indiana. It’s small, but I have yet to see an American zoo with a better variety of Australian wildlife.
For safari parks, I highly recommend Parc Safari in Hemmingsford, Quebec, just outside of Montreal.
Where did they go?