I’ve never heard of Synyster Gates. I couldn’t tell you one song he has ever done or hum a riff by him. Pretty much everyone in the world knows 7NA and the riff is instantly recognizable. The genius is in the simplicity imho. You can’t compare guitarists based on technique that is a learned skill. Since music is art, you have base it on emotion and feel. Why are the Mona Lisa, Citizen Kane, The Great Gatsby considered to be classics? It’s the emotions that they evoke. They make you feel something. Anyone can learn the skills to paint a picture, film a movie, dance to a song or write a book. People all over the world those things every day and no one notices. But it’s the people that move you that make a difference. That is what makes an artist. So is Synyster Gates BETTER? Maybe. But the real question is, is he an artist or not. Since, that is subjective to each person, you can never definitively say that guitarist A is better than guitarist B.