I'm getting this one for the simple reason that the reason I stopped playing the previous games were from a lack of people to play with. Animal Crossing's magic for me are the little things it does caused by other people living in your town, or friends of yours visiting your town. But getting people to visit your town all the time was annoying. The city area is great because it pretty much runs on WiiConnect24, and other features in the town itself can be enhanced by WiiConnect24 as well. Letters, villagers, contests, holidays, auctions, bottles, fashions, catch phrases, they can all be enhanced and it doesn't even have to be just your friends as it can be friends of friends, or friends of friends of friends, etc. And in the end, if my personal friends fail me now I have GAF.
So for me, the magic of Animal Crossing comes from all humans you play with and discover stuff with together. The problem with GCN Animal Crossing is that it became a very single player experience. Wild World ushered in online play, but you'd have to make time for it like a console game. It's portability once again made it an excellent single player game, and I couldn't leave it in much because I don't ever just play one game on my DS. I even ended up selling it off because of that. City Folk has the ability to realize the asynchronous multiplayer dream I have for Animal Crossing, and with everything I know about it for sure right now, it will at least come close to realizing that dream.
So get this for the multi, not the single, or else you really will be unhappy with it.