The older brother faithfully served in the home of his father exactly as the people in there day and age should, and as the younger brother should have acted. He gets the reputation as a man filled with anger and jealousy but would this type of man have stayed home so faithfully? I think not! Instead I propose that the older brother simply had a prodigal moment himself. His was not years long, nor did it cost him his livelihood, causing him to desire the pig's slop. His was a moment of anger and jealousy toward his recently found brother who was celebrated with the best of the farm (likely the older brother's labor, at least in part). Seriously, are you telling me you wouldn't feel at least a little angry and jealous if you were in his shoes?
If the father represents God and the younger brother represents the lost who are found, the older brother represents the followers who, while not perfect, continued to serve the Lord faithfully. I love the analogy of the church as a rescue boat, and the older brother would have most definitely been a crew member of the rescue boat. The man who momentarily gets wrapped up in rewards instead of the mission. This weak moment does not make this man a hateful, angry, and jealous man, it makes him a man who momentarily succumbed to the temptations of this world. In his day it was a party where the best crops, meat, and wine are served. On the rescue ship it is the man who brags about how many he has saved, instead of trying to figure our why he couldn't save that one guy he lost. In our life it is the people who get wrapped up in what the church is doing for them, or celebrate more for their favorite athlete than they do for a new Christian.
The older brother made a mistake and succumbed to temptation just like any other human. However, the older brother faithfully served his father without abandon, and the father's house would not have been the same without him. I think if Jesus were to have continued the parable the older brother would have continued to spew, sinfully, throughout the party, but as the party was winding down he would have gone into the house, welcomed his brother home, and celebrated the lost being found.