James Earl Jones had a great voice, but that's not why you remember him. A deep, powerful voice is fine, but James Earl Jones could do things with his voice because he was a great actor. He knew how to use the instrument he was given. He developed it with effort and practice. He brought his humanity to its use. That's why you remember him. His humanity and his craft.
All the times you pretended to be Darth Vader, you probably did what we all do when we're not James Earl Jones: you probably got as low as you could and did a kind of growly monotone. Maybe you put your hand over your mouth to really sell it. James Earl Jones didn't do that. Listen to his Vader sometime, with ears as fresh as you can. He's not a robot. He's not growling. There's power there, but there's emotion too.
And Vader is just one smidgen of his skill. It's a silly villain role in a silly kids movie about space wizards that, let's face it, no one thought would sell. He wasn't ashamed of Darth Vader, so you shouldn't be either. Without James Earl Jones, Darth Vader would have been less. But watch James Earl Jones act sometime. Even in a bad movie. The man brought it to every damn role he played. He was good at what he did, and he worked at it. Watch him be quiet. His whisper carries weight.
We have this idea that acting isn't really work, that being a movie star is just a matter of being famous. That's true of many movie stars, but probably fewer than you think. And James Earl Jones wasn't a movie star. He was an actor, of stage and screen and voice. I guarantee you, he worked at it.
We shall not see his like again.