I can just imagine all those 6 year old children watching the cartoon version of Darmok or The Drumhead.
If there is one series that is completely unsuitable for cartoons it is TNG.
Bull. Cartoons are not a genre, they're a medium. They can support storytelling at any level, just as live-action can, just as prose can, just as live theater can. Yes, there are some cartoons aimed at 6-year-olds, but there are others aimed at older children, at teens, at college students, at adults. (Perhaps you've heard of a little show called
The Simpsons? If you believe that show is either a) meant for 6-year-olds or b) live-action, then you're seriously in need of a reality check.) Many animated series have been acclaimed for their intelligence and depth and have loyal adult followings, including
Batman: The Animated Series, Gargoyles, and
Avatar: The Last Airbender.