I'll admit, the general premise sounds pretty lame, but once you get past the idea that it's literally nothing like the original Sims (and could easily, and probably should have, been given a different name) it's a surprisingly good series overall, though some games (e.g. Sky Heroes and the original) are weaker than others. I was given the DS version of the original when it first came out and I've been a massive fan of the series ever since - they're similar to Animal Crossing in that none of the games are particularly difficult and most aren't all that exciting, but boy are they relaxing. They are also extremely cute, and very funny.
The original My Sims
is worth a miss, but Kingdom and Agents are brilliant in different ways. Kingdom for the endless amount of time one can spend building and designing and Agents for the video game version of all those cartoons you loved to watch as a kid. I would definitely recommend both of them, especially Agents!