Why does this read like someone who didn't read the VN? Shirou is absolutely beautiful to contemplate, a hero and inspiration to all. An ideal everyone feels they could reach if only they were as selfless as he is, which of course no one is.
What makes it so great and beautiful is that he isn't admirable for his intellect, strength, or talent; it isn't innate goodness and kindness that makes him admirable, but a mindset he adopted.
What is enchanting about him is his dedication to perform things he feels are good. He isn't like Kiritsugu, who dreams of a perfect world. He just wants to see and do good things for the sake of the action itself being good, even if it won't matter or make a difference.
Above all the greatest beauty is that he lived his entire life doing what he thought was right, and when everything went wrong he didn't regret a single thing, because he knew it had been the right thing to do.
Even Archer would once again choose to become a Counter Guardian if presented with that situation. As much as he hates everything he did after, as much as he says he regrets becoming a Counter Guardian; at that moment, if presented with the choice between letting those people die or damning himself, he would once again sacrifice himself.
That the ending will be sad does not mean it was not worth following that path. There were things that matter mattered much more to Shirou than his own happiness. A beautiful ideal he chose himself.