I started with the original Animal Crossing on GCN. It was kind of funny because I initially had no interest in it, but my sister decided to borrow it from our cousin and I ended up playing it the most even though I don't remember being able to save since I had the regular memory cards and nowhere near enough space between them to make a town.
I first played Wild World, it was the very first game I brought with my first DS. After playing New Leaf I couldn't go back to wild world, I'd be entertained for hours playing NL but I haven't played it for almost a year now so I'd hate to see what my town looked like if I started playing again.