The Elephant in the Room. Monkey D. Luffy sets sail to find the legendary treasure, the One Piece, and become the Pirate King. The length is terrifying, but the journey is worth it.
How to tackle it: Do not binge the anime entirely. Watch the "One Pace" fan edit (which cuts filler) or read the manga. The manga is significantly faster to consume. Why is it popular? The world-building is unmatched. You will laugh, cry, and cheer for a rubber pirate and his ragtag crew. veohentai..com
You asked for "popular," but here are series that are critically beloved by hardcore fans but haven't quite broken the mainstream bubble yet. The Elephant in the Room
Humanity lives in fear of giant humanoid creatures called Titans, living behind enormous walls. After a Colossal Titan breaks the wall, Eren Yeager swears to exterminate every last Titan. The story evolves dramatically from a survival horror into a brutal war drama examining genocide, freedom, and moral relativism. You asked for "popular," but here are series
Why recommend it? It is the "Game of Thrones" of anime. Do not trust anyone. The plot twists are legendary, and the animation (especially the 3D maneuver gear sequences) is exhilarating.