I must admit, I only discovered April Ethereal FULLY recently, although I adored it before that, from 'I will endure...hide away' to the end is now one of my favourite sections of music ever.
When is fantastic. Just fantastic. Every riff, every beat, every lyric. It all fits so well.
The Amen Corner has an incredible intro, and incredible outro, and an incredible middle section. Therefore it's an incredible song. From about 4 mins to the end is one of my favourite passages of music.
Demon of the Fall is absolutely slayful. Such an atmospheric, brutal song, but with such beauty as well.
Credence is one of the greatest ballads ever written, IMO, but I had to vote for it, simply because there's not as much variation in the song.