What makes a great piece of music.

I often find my mind wandering thinking about what exactly makes me feel that a particular song or piece of music is great. There is both the lyrical and musical aspect of it. As a songwriter, it's both inspiring and frustrating to hear an amazing song. For example, the song; "A Day in the Life" by the Beatles. In my opinion, this is the Beatles masterpiece. I find myself thinking, "How could anyone come up with a song that f'ing amazing?" The frustrating part is I'm also thinking to myself, there is no way in your wildest dreams that you will ever write a song that good. Sad but true.
I think the best songs are the ones that seemingly fall out of the sky into the minds of musicians. The key is having the ability to turn that moment of "insperation" into a great song. The polar opposite of this are songs that are both lyrically and musically predictable. Songs that follow an already exhisting template. Music fabricated by well to do uninspired musicians who's sole purpose is to make a bunch of cash selling their image more than making original music. It's like a Rubics Cube. They can change the colors, but it will always be a Cube.