I've divided up my lists into top 5 short form, new and continuing (like Promised Neverland, with a season 2 confirmed or a series that's going into Winter 2020)
For new and complete, I'd say Astra Lost in Space, first and last episodes are a bit longer at 45 minutes each, but the story's really focused, yet gives you a lot to think about in the various topics it brings up, particularly utopia and such.
For ongoing, I'm a little biased, but I still say Demon Slayer is the best, even if it's going to be tricky to watch the movie even if CR gets it officially (though I like how they break it up into segments, if they imitate what they did with Digimon Adventure Tri's movies). The character focus is a bit skewed, but you get a sense of the world and how even what are meant to be deuteragonists (Zenitsu and Inosuke) have depth to them, Tanjiro and Nezuko much more the focus (because they're special and all), plus the effects are cool and the "demons" are presented in a variable manner, to say nothing of establishing a larger threat without needing to linger on him too much
And for short form, Joshikausei is a no-brainer, since there's pretty much no dialogue, but it's light hearted fun and the characters feel somewhat fleshed out in their dynamic and personalities.
