Details matter and being specific makes all the difference. Honoring an artist as "great" is an empty compliment and lacks integrity. How does this particular artist stand out from the others? What makes them "great" in your eyes?

Is it their vocal range, emotion on stage, music writing, the ability to sing and dance, knowing the right songs to choose to record, music production, talent on an instrument, willingness to shock the audience or their causes outside of music? 

There isn't a right or wrong answer. It is your opinion and your taste.