The Werribee Open Range Zoo is one of my favourite zoos. Yes, we can go into the whole argument about how 'animals need to be free' but the truth is some of these animals do need to be in captivity until their species' situation improves, people are the biggest threat.
It's a safari style zoo so the animals do get a lot of space, more than I've usually seen. The cafeteria food is so-so but I love how you can have lunch next to the meerkats, watch a keeper try to get a lioness to move, be stuck in a bus with strangers for 40 minutes whilst you check out giraffes and rhinos up close, see domestic chickens (are they not afraid of the lions?) and enjoy the beauty of these animals up close (that cheetah really looks like Hobbes!)
My absolute favourite zoo ever is actually the San Diego Zoo but I've never been so Werribee will do.