Here is how i see it: Every generation of children have a their own brand new, cartoon characters that become popular among that particular generation of kids, and are then promptly forgotten by the next generation. There is nothing strange about that, and there is no reason to complain about the fact that later generations dont know about such "flavor of the decade"-cartoons from our own childhood years.
However, throughout the history of animation, there have been a few cartoon characters that have managed to stay popular over several decades, finding new audiences among many generations of children. Think for instance about Mickey Mouse, Bugs Bunny, Tom and Jerry, Woody Woodpecker or Popeye. These characters initially became popular among in the 20's, 30's and 40's. The kids of that era knew and loved these characters, and so did the kids of the 50's, 60's, 70's 80's and 90's. And i find it quite sad that these characters have, only in the last ten to fifteen years or so, fallen out of relevance and are (with a few exceptions, such as Mickey) unknown among the newest generation of kids. And the reason why this is sad is because, due to these characters being well known among people of pretty much all other age groups (20 year olds as well as 45 year olds as well as 80 year olds), they belong to our societies public consciousness, they are characters that we can all recognize and reference, regardless of whether we grew up during WWII or after the fall of the Berlin wall. That is, we all, with the sole exception of kids who have grown up in the last 10 years or so. And i just find it sad that these cultural icons who have survived throughout so many different eras are now starting to "die out".