I still love cartoons such as the original Scooby Doo, Powerpuff Girls, and a handful of anime. I do think that the larger amount of anime appeals to the 12-16 age group, however, and that only a select few could really be art forms that adults of all ages can appreciate.
One cartoon that I find incredibly intelligent and absolutely wonderful for both kids and adults is Samurai Jack. If you haven't seen it, you are missing out hardcore. I bought all four seasons on DVD.
Although the series never had a proper conclusion, one can still hope.