"The Greatest of these is Love: Why?"
Seriously? You're making me justify St. Paul's conclusions?
Just kidding; I enjoy the intellectual stimulation.
There are a number of reasons why Love is a greater virtue than Faith or Hope. For one thing, Faith and Hope are both temporary virtues: we won't have either in Heaven, because both depend on things unknown. Faith is "the belief in things not seen," the divinely-inspired step extension beyond the intellect. Hope is the expectation of God's goodness; the trust in what God will do in the future. But in Heaven we will see God face-to-face, so there will be no need of Faith, and we will experience all bliss, so there will be no Hope. But there will still be Love, and indeed the fulness of Love. Faith and Hope will both have served their purpose, but Love will only just be getting started.
Another reason is the fact that Love, more than the other two, deals with the will; the core of our being. Faith and Hope both deal more with the intellect and only are tangenitally attached to the will. Love, however, is entirely an act of the will and so has the greater effect on our souls.
Finally, Love is the virtue of God, while Faith and Hope are virtues given by God. This is related to the first point, but when we are acting out of Faith we are not being like God, since God has no Faith since He is all knowing and no Hope since all time is present to Him. To Love, however, is to be like God; to live in His life. Therefore, since Love is more God-like, Love is greater.