How are the prophecies for Banquo paradoxical?

In scene three, when Banquo receives the three predictions from the witches he is told that he will be "Lesser than Macbeth, and greater / Not so happy, yet much happier / Thou shalt get kings, though thou be none." This is a perfect example of a paradox (something not as it seems) and filled with double meaning. Banquo, for example, will never be king, but he will father a line of kings. As for Macbeth, we see that even though he should be far happier than Banquo because he's king, Banquo will be the happier of the two because he carries no guilt.