I know anime is known for being serious and dramatic, but american cartoons are typically about comedy (even if it's adult humor) and you hardly ever see serious american cartoons, and I love the few I have seen. I really admire this concept, and would love to see more "non-anime" cartoons take a serious approach.
A few serious cartoons I've seen are:
Spawn: the animated series
Heavy Metal/Heavy Metal 2000
Fire and Ice
Some of the DC hero cartoons
I'm looking for cartoons that involve