For those thinking Zoo Tycoon is just for kids, you're wrong! I'm 16 and I love it!
I am sure it would appeal to adults aswell.
In my opinion, its just a relaxing, stress-free game that you can go and just sink into when you feel the need.
You can create animals and they will have babies and they are believe it or not quite cute!
It is also a great game to buy children for birthdays or what have you as it is totally innocent game where they can't go wrong.
It is quite hard to get the hang of the controls etc, but once you watch the tutorial, you'll be fine. You can create animals such as dolphins, orcas, tapirs (the baby tapirs are beyond cute), basically every animal you can think of, including dinosaurs with the included dinosaur digs and marine mania parts.
Go out, buy, and enjoy!