Compared to most zoos, Lincoln Park has animals rather close to the observers. The zoo is compact so you can walk it without getting tired (for adults). There's not a huge collection of animals, but there are some real highlights. My favorites are: Seals; tigers if they're out; the gorillas- always interesting; the monkeys; the frogs; and of course the super-speedy penguins underwater. I also like the flamingos when they're active, they're so exotic. The whole children's zoo area is much better than most similar ones.
Dislikes- few places to site down for a respite; and it can be very crowded in the summer. My favorite times to go are fall and spring. Oh, and at Christmas they have a great light display- there are music-synchronized light shows, it's fun even for the kids.
Overall- quite a bargain, it's free. I don't think I've seen any comparable zoos that don't charge admission.
If you're in Chicago, you really should get to the zoo- and if you have an hour or so, go to the Conservatory next door (literally 100 feet away) and see the koi and all the exotic plants (and flower shows). The Conservatory is especially nice in fall/winter, it's nice and warm and no wind, and there's always a beautiful holiday show. (With model trains).
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC