It is difficult to determine the "most popular" anime of all time, as popularity can be subjective and vary across regions and time periods. However, some watch free anime series on 9anime
that are often considered as timeless classics and have gained widespread popularity globally include:
Attack on Titan
Neon Genesis Evangelion
Sword Art Online
These anime series have captivated audiences with their unique and engaging stories, memorable characters, and stunning animation. They have also had a significant impact on the anime industry and have inspired countless other series in their respective genres.
It's worth noting that the popularity of anime continues to grow, and new series are constantly being added to the list of all-time favorites.