See, I have only played Animal Crossing: City Folk, and I am wondering what the other titles are like because I might get them. What I'd like to know how the other games compare to City Folk.
Wild World is a great game because it's portable, although the actual town in the game is boring since it's smaller and there's not as much to do.
PG is my personal favorite game in the series. Some newer AC players may consider it a 'step down' from the other two games since it was the first game in the series, but it's a great game with some things not found in the later versions (police station, island, acres, train...)
If you had to get one I'd recommend PG.