I don't think people realize what HAS changed. This game keeps classic gameplay, yes, but it still adds plenty.
I've played all the other Animal Crossing games, so although I haven't played this game an extremely long time yet, I do know enough to write a good review of it.
--What's changed?--
Quite a bit has changed here (although the basic principle and gameplay is mostly the same), and not many people are appreciating what has changed. In the village, real holidays are back (this is a change from Wild World), there are now four houses spaced differently all throughout the town. This gives you a better opportunity to live near something you want to, and I like it.
There are now motion controls when fishing, using the net, etc. It's a nice change, and I like the control system. The nunchucks are optional, however, I recommend you use them, it makes it much easier. The town gates have changed a little, and there's now a bus stop to head to the city. I haven't upgraded my house yet, so I can't tell you how that's changed. Oh, and Lyle, Redd, Shampoodle, and some other special characters will no longer appear. They are now in the city.
Speaking of which, let's talk about the city. Once you board a bus in your village, you will be taken to the city. It is arranged in a circle-like pattern with various shops. There's Redd's shop, which won't be available from the start. There's a theatre. That's where you can pay 800 bells to watch Dr. Shrunk perform and get a new emotion. (His jokes are terrible, just to warn you. Haha.) Next, there's an ATM where you deposit and withdraw from your bank account, pay your mortage, etc. Next you have the HRA, where Lyle will tell you his life story and then will let you join the HRA. You next have GracieGrace which is a store that sells extremely expensive, but nice, stuff. You then have an auction house, where you can put items up for auction, or bid on others. Next you have a shoe-shining place. Then there's Shampoodle who will do your hair. Or, you can choose to look like on of your Miis. It's a very nice feature. Then you have Katrina's, who will do your fortune, or your town's charm.
Sometimes in the city, there will be a guy who will give you a prize. You can get balloons, bubbles, etc. This is a new thing, and is pretty fun to get. As you can see, the city may look small, but there is quite a bit to do!
There's probably some new stuff I'm missing, but I'm just trying to show some of the major new features, and to show that quite a few things are different.
--What's the same?--
The principle of the game is the same. You're a guy/girl moving in to a town with animals that has no money, has to work for Nook and pay off a mortage, buy items, grow trees, fish, catch bugs, etc. Things have changed, but if you're looking for a completely new Animal Crossing experience, this probably isn't it. I've owned all three games, and let me tell you, City Folk is still very fun, even if it's still the same premise. Oh, and if you don't want to start completely over, you can transfer your character and catalog over from AC:WW. I chose to just start over anyway.
--Graphics?--
Well, it looks like an Animal Crossing game. What do I mean by that? It looks typical of the Animal Crossing graphics you've grown to love. Now, I'm not saying they haven't improved. The colors are vibrant and very nice looking. The graphics, of course, have gotten sharper and better looking. Animal Crossing City Folk is a very nice looking game in general.
--Online?--
A lot like AC:WW, but improved some. Anything you type appears over your head, helping others find you. Plus, it looks better. You have the option of WiiSpeak, which is voice chat, plus you can type with a USB keyboard. (I highly suggest either WiiSpeak or a keyboard because it is annoying typing with the WiiMote in this game in my opinion.)
-Overall--
Are you looking for a brand new and different AC experience? Well, this isn't wildly different.
Are you looking for an AC with better features? This definately fits this category.
Are you looking for a very fun game in general? This fits great. This game is VERY fun.