Talented voice actors, even when they had bad cues and silly scripts.
Everyone is distinct and easily identifiable when they speak.
Even though Linda gets a lot of hate, she's not a bad actress, she was just having to try and emulate Terri Hawks and was incapable, so it made her performance in early episodes sound busted.
As Serenity, she was perfect, and I think her serious scenes were quite good as well.
It's also partially/mostly responsible for the success of Sailor Moon in the English speaking world...and to be honest, anime in general.