John 14:12 states, "Verily, verily, I say unto you, He that believeth on me, the works that I do shall he do also; and greater works than these shall he do; because I go unto my Father."
Jesus Christ healed the sick, even those with leprosy. He made the blind see and the lame walk. Even those with life long illnesses and disabilities were cured.
He commanded the storm to stop and it stopped. He commanded a tree to die, and it did. He had nets so full of fish that they had trouble bringing them in. He had a fish give a coin to pay taxes. And to top off his visible miracles, he brought back Lazareth from the dead. And how can we even equal his work of the atonement, let alone do a greater work?
Why then did Jesus say to his apostles that they shall do greater works than him?
I believe the answer lies in a better examination of the statement. He has stated that the reason why they shall do greater works than him is, "because I go unto my Father". So how does him going to the Father make it that the apostles could do greater works? The answer must surely be that when he said "greater" he didn't mean the greatness of each individual work, but greater in number. Because he was only doing works for three and a half years, and then was going to the Father, the apostles would have opportunity to do a greater amount of works, having decades to do them in.