Leaping from the Gamecube to the much less powerful DS, Animal Crossing had to make a lot of sacrifices. Smaller towns with less villagers, very few holidays, and even less space when writing letters. At the same time though, it would refine the image of the original effectively enough to set the direction for the series going forward—this is where the general look of the characters (goodbye, weird mandatory hats!) and the world (hello, cylinder!) were solidified, along with certain staple mechanics like watering flowers, shooting down balloons, and even simpler stuff like the introduction of the town hall, the expansion of the museum (plus Blathers now being able to identify fossils himself), and the introduction of headwear and actual decent item storage. Not to mention both local and online multiplayer! For such a small game, Wild World really gave a lot to the series.
Despite being a smaller package, I find it hard to view Wild World as particularly lesser than its predecessor. In fact, its portable nature has led me to pick it up again much more frequently over the years, spending a few days cleaning up my town only to put the game down again a couple more days after, repeating the cycle. It's the unavoidable charm that this game bursts with that keeps bringing me back to it—I'd argue that this is one of the best written games in the series, with the silly (and sometimes brutal) dialogue of the villagers, especially in their interactions with each other, never failing to make me smile. That as well as my fruitless quest to catch all the fish and bugs (sigh… maybe one day… I did just complete the fossil collection after all, so there's hope).
Is Wild World a game with much to do? No. If it's heaps of content you're after, you're in the wrong place—but then again, that was never really what Animal Crossing was about. Wild World is a game meant to be played every once in a while over the course of years; playing too much in too short a period of time will only burn you out. It's not a style of game that resonates with everybody, but as far as I'm concerned, I find it to be a comforting little pastime for the scattered handful of weeks each year I inevitably come back to it.