Non-basketball, but... in reading the full ESPY list, I have a beef with Shaun White as best Oly Moment. I acknowledge that there was a comeback component to White's performance, but if they needed something with an inspiring American bias, I think Jessie Diggins and Kikkan Randall's Nordic gold was more deserving. Incidentally, Randall was recently diagnosed with breast cancer.
Having said that, in my mind nothing compares to Czech Ester Ledecka's wins in two different sports, skiing and snowboarding. Once you get beyond "sliding down a snow-covered hill on slippery plank/s," there's not a great deal of crossover between these two disciplines. Her disbelieving reaction to her skiing win was the defining Oly moment for me.
Completely unrelated to the ESPYs, but a basketball oriented comment... how bout' Liz Cambage!