The GCN Animal Crossing is the best. I played it obsessively for a long time. Wild World came around and made some bad changes (in other words, changes just to be changes. They weren't necessary and just changed the atmosphere) but it also added quite a bit, still it got a lot more boring than the GCN version ever did.
City Folk/Lets Go To The City? Don't even get me started on that game, it's not a good idea. I'll just say that if Nintendo wasn't even going to put the slightest bit of effort into making it a sequel worth purchasing than they shouldn't have ever even made it to begin with. It singlehandedly took my opinion of the series, the Wii, and Nintendo altogether down significantly.