There's no precise count. The number is constantly changing as new manga are published and some become less popular. But you can find a huge variety across different genres and styles.
The number of comic books is simply astronomical. Different countries, different styles, and countless series and issues make it impossible to come up with a specific figure. But it's safe to say there are millions upon millions.
Oh yeah! Sailor Moon manga is widely popular. It's loved for its themes of friendship, empowerment, and adventure, which resonate with people everywhere.