Most of my favorite parables are in Luke. I like how the parable seems to focus on the son who was lost, but eventually the emphasis rests on the son who stayed home.
The son who went astray had a temporary problem. He was humbled, then recognized the need for his father, and returned a changed man. The son who stayed home had a more permanent problem. He felt no need to change anything about himself. He felt entitled to what his father had, but he didn’t value what his father valued: his father’s son.
The father’s money had been squandered by the wayward son, and yet the father came running to greet him on his return. His son was worth more than the money. The son who stayed home had lost nothing of his own, and yet he was offended that his father should rejoice over his brother.
This parable, and several others, were the response Jesus gave to the Pharisees and scribes when He was criticized for eating with publicans and sinners. Those sinners had found the kingdom while the blind Pharisees had been leading the blind.
I hope to always identify with the lost sheep seeking a Shepherd and the humbled son returning to his Father. To identify with the son who stayed home would be to misunderstand the parable.