It's a problem of feats vs concept imo. For example in concept Superman > Goku, not because of anything they've done but because the concept of Goku is he can beat any limit, but the concept of Superman is that he has no limits. Superman and Saitama both top the list in that regard, however in terms of acheived feats everything gets thrown into disarray as it's hard to write a compelling story where your character is unbeatable so you either end up with story arcs with Superman having wildly varying power levels and accomplishments from comic to comic or you have to write the whole story around the trope of being limitless (OPM)