Jesus promised that those who believe in him would do great works and pray with confidence (see 1 John 5:14). This would happen after Jesus returned to the Father, when he sent the Holy Spirit to give them strength and guidance (John 14:16).
The greater things will not surpass what Jesus did. Instead, ordinary people will do these works because the Holy Spirit gives them power. God promised that in the era of the Spirit, he would bring his kingdom and power into the world in a new way.