Well, 'Sword Art Online' could be comparable. It features a virtual world and character development similar to what you might expect in 'The World Ens Harem'. There are also adventure and relationship elements.
I think 'That Time I Got Reincarnated as a Slime' might be somewhat similar. It has an interesting fantasy world and diverse characters.
Maybe 'No Game No Life' is similar. It has a unique world setting and complex character interactions like in 'The World Ens Harem'. Plus, the storylines are both engaging and full of surprises.
I think 'Redo of Healer' could be somewhat similar. Both have elements of a post-apocalyptic setting and complex relationships.
I think 'Golden Time' is somewhat similar. Both have complex character relationships and emotional developments.
One manga that comes to mind is The God of High School. It shares some similarities in terms of action and character development with Eleceed. Both have exciting battles and characters with unique abilities.
One manga that could be similar is 'Fushigi Yuugi'. It has a fantasy setting and complex character relationships like Inuyasha.
I think 'Kuroko's Basketball' is somewhat similar. It has intense sports action and character development like Bluelock.
I think 'Game of Thrones' manga might have some similarities. It has complex character relationships and strategic elements like in Othello.
You could check out 'The Quintessential Quintuplets'. It has a similar light-hearted and romantic tone, and characters with their own quirks and development, like in 'Renting a Girlfriend'.
You could check out 'Naruto'. It has a similar mix of adventure, friendship, and growth as seen in Fullmetal Alchemist. Although the settings are different, the core themes of determination and self-discovery are quite comparable.
One manga that could be similar is 'The Gamer'. It features a protagonist with unique powers and an engaging adventure similar to 'Strongest Leveling'.
I think 'My Little Monster' could be similar. It has a unique dynamic between the main characters, like in 'The Girl and the Geek', and the plot has its share of cute and unexpected moments.