I totally agree with the idea that you can have multiple kids in the same family raised the same way, with same methods and the same values, and who knows why they all still turn out different.
I read your post from yesterday and it's refreshing to see someone openly admit that maybe they dropped the ball somewhere along the way, but also realize too that sometimes there is only so much we are in control of. At some point kids start making their own choices about how they live their lives and we can't always feel responsible for the decisions they make. We can't always know how much our influence plays into the choices they make. Hindsight is always 20/20 and it's easy enough to play "Monday morning quarterback" with our parenting decisions. I think the thing is now is that you need to start cutting the cord more with your son so he has no choice but to do more for himself. He may get angry about it, but it is the nature of those who have been enabled, once they are no longer being enabled, to get angry at the enabler. If he starts giving you a hard time, remind him that you fulfilled your obligation - he had food on the table, clothes on his back, a roof over his head, educational opportunities, medical care, was protected from harm, and was shown love repeatedly. What he decides to do now is up to him.
I have my own story regarding my stepsons, who are now 17 and 18. The 18 year old just finished high school this past spring, is currently working part-time flipping burgers, and talks about going to college but hasn't taken any of the necessary steps to actually make it happen. The 17 year old is a junior in high school and thinks he wants to study culinary arts but gets mediocre grades when he is capable of much, much more. They are both nice, good, kids, but unless they start setting some concrete goals in place and see them through, they are going to slip through the cracks and not have much of a future. All their lives, their mother made things easy on them - she didn't want them to struggle, she didn't want them to feel like she hated them, she wanted them to be happy all the time. She figured they would have to deal with the real world soon enough and for now they should "just be kids" and enjoy it. Her opinion was that as long as they weren't juvenile delinquents and engaging in criminal behavior, they should be able to have and allowed to do whatever they wanted. And now they continue to expect others to make things easy on them, and for everything to happen for them with minimal effort. The real world is here and they don't know how to handle it. The younger one in particular seems to have more of a sense of "entitlement" - when we took them on vacation with us last year and he kept copping an attitude about everything, we reminded him that we didn't need to take him on this trip, and we didn't need to take him on future trips (they live with their mom). He tried to argue back that he was our kid, and we "HAD" to take him - ummm, guess what? NO WE DON'T! And one memory I have that particularly stands out in my mind is one time when they, their mother, and myself went out to lunch and the boys were around 6 or 7. While we were waiting for our food, they both got activity pages with stuff on them to do and crayons. The younger one looked at his and whined that he didn't know how to do any of them. If it were up to me, my response would have been to either show him how they were done, or tell him to flip it over and draw a picture on the back. But their mom was with us, and her response was to CALL THE WAITRESS OVER AND ASK FOR A DIFFERENT ONE for her son! I couldn't believe it but I kept my mouth shut. Because I didn't have kids of my own at the time and I knew the quickest way to piss of my husband's ex-wife was to question or criticize or say anything about anything she did when it came to those boys. I'm don't doubt that in her mind she thought she was doing to right thing for her son. But long-term, it seems to me that such actions don't teach them anything or do them any favors, except that other people should bend over backwards and be inconvenienced in order to cater to their every need and whim.
Another time they wanted an XBOX game system and their mom told them they had to save up their money for it. God Bless them, they saved all their birthday money, Christmas money, and extras for over a year to get that XBOX. They were going to buy it after Christmas when it went on sale. Then their mom ended up buying it for them, paying full price so they could be surprised on Christmas morning when they found it under the tree. She thought she was being nice, rewarding them for saving and being patient, and now they could use their savings for more games and other things. I thought she totally blew an opportunity to teach them an essential life lesson.
THAT is how kids grow up feeling entitled!