John is the model of the disciple who leans into the heart of Jesus. Like Mary the sister of Martha (see Luke 10:38), he has "chosen the better part, which will not be taken away from" him.
The Beloved Disciple at the Foot of the Cross: 3rd Day of Christmas
John is beloved because he is a disciple who himself loves much - so much that he alone of the Apostles follows Christ all the way to Calvary and stands with the Blessed Mother and Mary Magdalene at the foot of the Cross. He is our model in loving discipleship.