As we get older... I don't know a single person who has devoted their life to musical theatre who hasn't had a couple of misses as well as a bunch of hits. The misses, we learn a great deal from them.
For me, when you are talking about perfect songs, you're talking about Gershwin, 'Someone To Watch Over Me.' Or Larry Hart and Richard Rodgers. Or some of the great Cole Porter songs, whether it's 'Night and Day' or some of the comedy songs. Or Irving Berlin, of course.