Dragon Ball Z (and its other shows) are my favorite because they were the first anime/manga i had ever read/watched. I really like the story and Goku is one of my favorite anime characters of all time.
picture source: Google images: pintrest
Hunter X Hunter is one of my favorite anime because of the story. The story fits really well together and all of the arcs are really smooth and lead to one another. You can also see how different characters struggle and how they improve.
picture source: Google images by josecrobledo on DeviantArt
Demon Slayer is one of my favorite anime because of the animation and action. The anime is very fast paced and the story is very good. The animation is also really high quality and all of the characters are good.
image source: Goggle images, drawing by Chapardeur