I think it is rather clear there are no completely perfect songs. However, I do think there are moments in some songs that are absolutely perfect.
The Bends - 3:00 - 3:01, with the two piano hits.
This Is The Dream of Win and Regine - 0:09 - 0:25
Arcade Fire - Wake Up - 0:22 - 0:44
Play your Part Pt 2. - When the beat and the piano from Faithfully come in, but the Pop, Lock, and Drop It vocals don't yet.
To name a few.