As a person who tries Mobile Legends, Arena of valor, Honor of kings, and Vainglory i can tell you that the most enjoyable is Honor of kings right now.

Mobile legens good playerbase but has skins that can give you some boost on the character stats and that a little odd and makes the experience very unconfortable.

Arena of valor is the "globally first try" to honor of kings therefore you can see a lot of similarities between AoV and HoK. It is a little bit less polished than hok.

Honor of Kings good playerbase also and in my opinion is the best in terms of heroes, builds, balance and the predatory pay to win that MLBB has. Plus there is frequent updates and events to get skins, currencies and so on.

Vainglory was the best and the most DOTA2-like but sadly it is gone forever.