The premise: your the 'tycoon' and you build and maintain an amusement park.
The goal: to have so many guests in your park and a high enough rating to win the park.
The addiction: everytime you achieve your goal<so many guests & a high enough rating by a certain date> you are given a new park to play in.
There are many different locations, settings and themes. The guests in your parks have different likes and dislikes, some of them actually throw up on your paths.You must hire staff to care for the park .Handymen to clean up<mostly vomit>,entertainers, security and mechanics to fix and maintain your rides.
The game is very involving and time consuming but a real treat.My five year old daughter is always playing.She loves to plant gardens and create hedge mazes for her guests to enjoy.
There's an expansion pack called Corkscrew Follies which is just as great as RollerCoaster Tycoon. If you just want to give it a try there's a free demo you can download at www.rollercoastertycoon.com Beware! If you don't plan on buying the game don't download the demo! You will become addicted and get frustrated when the demo shuts down.I know ,that's what happened to me.