Animal Crossing: City Folk is a decent, addictive game that doesn't really add anything new to the series.
When you begin the game, you'll have a tiny house in a rather uninhabited town. The major shop in the town is very small, and the museum has absolutely nothing in it. This is where you come in; the more you shop at the store, the bigger it becomes until it just about becomes a super-store, you can pay off your mortgage for your house to make it bigger and bigger until it's almost a mansion, and you can fill the museum up with any fish or insects you find (there are a total of 64 different kinds of both), as well as fossils you find in the ground and rare paintings you buy from certain stores.
That's not all they allow you to do though; you can turn your town into a paradise complete with fruit orchards and coconut trees lining the beach. There's a wide variety of flowers you can find and plant, and the fact you can create "hybrid" flowers by taking good care of your flowers and planting them next to eachother even makes gardening interesting, since so many people would just love to have black, blue, or golden roses all over their town.
The main addition to Animal Crossing this time around, however, is the city. After a few minutes in the game you'll be allowed to take a bus to the city whenever you want, broadening the horizons of what you can do even more with all the different shops there. You can get your hair changed to customize your character at Shampoodle's, get your shoes shined by Kicks to change their color, join Animal Crossing's version of the Black Market at Redd's Shop, learn facial expressions at the marquee, and that's not all. You can get your fortune read, sell things at an auction house, or go shopping for rare and exclusive furniture and clothing at Gracie Grace's shop.
Don't think for a second that Animal Crossing: City Folk is nothing but good news, though. Walking around on the grass in your town, which is found everywhere, slowly wears it away. This was made to help you create paths, but it has a completely negative impact on your town; within a month of playing the game you'll notice the fact that your town is starting to look terrible, and some people have lost all their grass all-together, leaving your town a barren waste land. It takes several months to grow the grass back, too, and that's if you don't walk on where you want it. For a game where you're encouraged to explore your town, it's too bad that you're punished for it.
One of the greatest new additions in the last installment was the inclusion of neighbors' pictures; when you became great friends with the animal residents in your town, they'd happily give you a picture of themselves you could display in your house. In City Folk, however, this addition has been removed. With it gone, there is no longer any reason whatsoever to be nice or even pay attention to your neighbors.
In the end, Animal Crossing: City Folk is a decent game that anyone new to the Animal Crossing universe should definitely check out. If you've been around for the other installments, however, don't bother picking this one up off of the shelve.