Are non-Japanese animation allowed in this thread? Because if it is, there's only one possible answer to this question for me.
Pirates of Dark Water.
It was cancelled before they got to finish the main arc of the story, and I am SO SALTY about this. Yes, I know it's been 20 years - BUT STILL! It was equal parts adventure, scifi and mild horror (a dude gets eaten by a monster in the first episode - crunching sounds and all!), it had a main cast that was 100% people of colour, and the costume design was like someone had taken one look at Ziggy Stardust and gone "Yes! This is amazing! All it needs is an extra pinch of scifi!" and just run with it. <3
... I have unresolved PoDW-feelings, okay?