Detroit Zoo not only has some outstanding exhibit complexes like Arctic Ring of Life, Great Apes of Harambee, Amphibiville, Holden Museum of Living Reptiles (85 species and 250 animals) but also some creatures rarely exhibited in American zoos: Bush Dog, Drill, Aardvark, White-Lipped Deer, Przewalski's Wild Horse, Takin, Lesser Kudu, Texas Blind Cave Salamander, Japanese Giant Salamander, etc.
I really enjoyed Detroit Zoo, and I agree they have a lot of really great exhibits. Arctic Ring of Life is such a gem, and was well worth the drive from Chicago to see. Some other highlights for me were the tree kangaroo and red panda exhibits. I found both of those exhibits to be pretty great.