Your Sims live, rather than in an ill-defined city as in some previous console Sims games, in an adorable little town with lots of places to explore. Just like in Animal Crossing, new characters will move into the town. Unlike AC, however, many of them serve specific purposes (running stores, for example) and you have the chance to build their houses for them when they arrive.
Of course, you have a lot of ability to customize your own character - in a much more exciting way than simply changing your clothes. The MySims characters are customizable in pretty much every way - though there's no ability to turn them not cute. They'll only let you go so far.
We were taken with the adorable graphics and the increased depth of the game over Animal Crossing. Whether it seems addictive or more like a chore will only be something we'll see when we get more time with the game. Animal Crossing was always addictive; MySims might be trying to add too much to the formula. On the other hand, we always hoped for a little more to do. We'll see.