As weird as it might sound i think that there cannot be “good” if there is no “evil”,what makes someone good is

because they are the opposite of evil,and what makes someone evil is because they are the opposite of good...

so yes there cannot be good if evil never existed because what we call “good” would look like a normal behaviour if there was no “evil”in the world,people take

you as a good person because they believe you are not an evil person,you cannot be evil and still claim to be a good person...