To your first point: He earned the medals through hard work, perseverance, and talent. He had a fair shot just like the rest of the swimmers. He earned 18 gold medals, and 22 medals overall over his career. The physical sign of his prosperity is the gold medal and the money that comes with it. But the real sign of his success is the sense of accomplishment. The fact that he got to travel to Athens, Beijing and London to compete for his earnings. He also had the chance, as I learned from a recent internet post, to sow his wild oats all over the olympic village as the place is basically one big orgy all the time during the olympics. So there are three things he has earned. Gold Medals and Money, Sense of accomplishment, and beautiful women in exotic locales. There are also sponsorships with corporations like Subway and things like that too.
Anyways, so Phelps is the all-time richest man in Olympic history. Should he hoard all of that wealth to himself? No. He should pass on his knowledge to the next generation so that someone from, I hope, the USA breaks his record one day. Pass on the sense of accomplishment. Pass on the olympic medals via tutoring the next young generation of swimmers. He doesn’t have to give away his physical golds, he just has to realize that his time to compete has come and gone and now it is time to reward those who are following in his footsteps by teaching them how to earn his medals. Then they will be the ones with sponsorships. Then they will be the ones going to exotic locales and sleeping with a whole flock of men and women(unless you are Lolo Jones who I greatly respect). Whatever rewards he has reaped from the games he can pass on through any number of ways. Maybe set up a charitable foundation with his earnings that benefits poorer children who can’t afford swimming classes. Something like that.
To your second point. He may have swum the races but he was not the only one in the metaphorical pool. His coaches from age, what, 2 on up had to recognize and shape his talent all the way from beginner classes through today’s final relay. He was the clay, they were the craftsmen. His coaches, parents, friends, girlfriends all helped to mold him into the fine-tuned machine he was, is, and may be if his Mom gets her way and he competes in Rio. Yes his name is the one that will be remembered, but it took a great many people in his entire life to make him the star he has become. So in that respect, he did not win the medal. They did.
It has been, is, and always will be a team effort to get from A to B.