This is an impossible task, should be 50 best songs at least 😉 As of today... in pop/rock music Innuendo by Queen. Someone else above explained why 😉 Its complex and elaborative but not boring because it contains several thematic changes and changes in modulation . Like very few musicians were and , even more now, are able to create almost 7 min long song that is recognisable at any given poinst of it and keeps you invested till the very last note. I fell in love with queen and this particular song when i wasn't able to understand texts of the songs in english, so it was just a pure magic of music. But when i finally learned english so i understood the text of Innuendo - it was like a stroke, bc text was also perfect. I think a lot of ppl underappreciate Queen's texts. They are amazing , full sentences, finished thoughts, deep and universal messages. In classic music , it prob would be Bach - Keyboard concerto no 5 in F minor (esp. in Glenn Gould's interpretation). because it allows to re-connect with yourself and other ppl. Bach was basically creating music for transpersonal experiences.