The Outsiders is told from Ponyboy's perspective, so readers don't have a good understanding of Darry until later in the book when Ponyboy finally better understands Darry. What we do know early on in the story is that Darry has a lot going for him. He is smart, athletic, and a very good looking young man.
Darry was too smart to be a greaser.
Ponyboy knows that if any of the greasers has a chance for getting out of their lot in life and making something of themselves, Darry is the best bet. College is a realistic possibility, because his athleticism and smarts are both things that could see him into and through a college degree. From that point forward, the possibilities for Darry to have a solid career are nearly endless.
Unfortunately, Darry, Soda, and Ponyboy have been dealt a very tough situation. Both of their parents were killed in a car crash, and Darry was forced to make a choice. He could look after himself, or he could look after his family. There was a real possibility that the brothers could have been split up and sent off to different foster homes.
If the judge decides Darry isn't a good guardian or something, I'm liable to get stuck in a home somewhere. That's the rotten part of this deal. Darry is a good guardian; he makes me study and knows where I am and who I'm with all the time.
Ponyboy's admission shows readers that he is fully aware that Darry gave up a bright future so that the family could stay together. Ponyboy has a lot of emotions about this situation. On one hand, he is very humbled by Darry's decision; however, Ponyboy also feels guilty, because he thinks that he and Soda are holding Darry back. Ponyboy does end up realizing that Darry's decision to care for the family was based on love for his brothers rather than out of pure obligation.
Darry did care about me, maybe as much as he cared about Soda, and because he cared he was trying too hard to make something of me. When he yelled "Pony, where have you been all this time?" he meant "Pony, you've scared me to death. Please be careful, because I couldn't stand it if anything happened to you."