Thats the beauty of the Johnny Thunder thing, by the time they come back and peoples memories are restored Supermans been cemented as "The first" even if its just for his generation.
Theres also the fact that he's arguably more powerful then the JSA (depending on membership) and that unlike them he's fully open with his identity, no mask or anything. Re member to a good majority of the DCU Superman is Kal-El a friendly alien who was raised on earth but helps humanity out of a sense of decency and lives in the arctic.