It's one thing having a great song, but I think for me if you take it to the next level... say you had a guitar and a vocal, and the song was amazing but the vocalist wasn't that great and it just was a guitar and vocal acoustic track, switching that to something like an amazing voice singing the exact same song with the instrumentation being really nice and lush or unique in some way and interesting and diverse... I think it's all about the instrumentation and textures in the sound.