Gotta love the original Jonny Quest (IMDb rating 8.0). The first cartoon series to air during prime time, because of its serious themes. They made an effort to use real places, to depict some realistic animals, and even gave some of the villains realistic motives.
And a LOT of villains got killed, some in pretty awful ways.
Some of the science fiction was realistic, some fantastic, and much of it plausible. Their depiction of ethnic groups was... ethnic.
And don’t forget the superb music and incidental sounds.
Even the opening credits were both scary and incredibly cool.