This might sound like an exaggeration, but it's not. There are many classic Star Trek episodes, IMHO this is the best of them all.
Maybe it's because I'm older now, been watching Star Trek since the original series was the entire Trek universe. Maybe it's because I admire Klingons, esp their old ways. Maybe it is because I'm a man against time, but I think this is the best episode of Trek ever made.
Sacrifice, honor, overwhelming odds. It's the best of the best. Not a huge production budget, no amazing CGI effects, no massive sound stages or production facilities, just good acting, plot and classic theatre.
Savor the fruit of life, my young friends...