Obviously Jack Swindells, a man for whom the word "legend" was invented. John Owens was to my mind the best player in non-league never to play league football. He could have walked into many league back fours of his day, and he, Jack, and Jeff Johnson are the first three names on my all time Alty greats team.
Among players who didn't wear the red and white, I'd nominate Stuart Pearce, Cyrille Regis who started at Hayes, Paul Mariner (Chorley), and going back over 50 years Warren Bradley. For those who don't remember him, Warren was a schoolteacher (like John Owens) who played for Bishop Auckland when they were amateurs, and also won 11 amateur caps for England. After the Munich disaster he signed for United on emergency papers, and featured on the right wing for them. He made 62 appearances and scored 20 goals, and then went on to win 3 full England caps. So good that I can just about forgive him for playing for Macc and Vics at the end of his illustrious career !