Well, in this life I've seen ev'rything I can see, womanI've seen lovers flyin' through the air hand in handI've seen babies dancing in the midnight sunAnd I've seen dreams that came from the heavenly skies aboveI've seen old men cryin' at their own grace sidesAnd I've seen pigs all sitting, watching picture slidesBut I've never seen nothin' like you
And "I heard" in the second:
Well, I heard the crowd singin' out of tuneAs they sat and sang "Auld Lang Syne" by the light of the moonI heard the preachers bangin' on the drumsAnd I heard the police playin' with their gunsBut I never heard nothin' like you
The repeated "I've seen" and "I heard" illustrate the amount and variety of the speaker/singer's experiences and emphasize the contrast between all of them and "you."