We already know that Blast is nothing compared to Saitama: remember that Blast fought with the main guy from ninja village and had to recover after that. Saitama just onepunched this ninja-village guy, as he always does. I suppose that there is a speed limit which is accessible to many: perhaps Sonic (now), Flash, Blast, Blue, Garou and others can achieve the same speed as Saitama, but defenetely not the same power. Moreover, there might be a funny twist in the future that Saitama has never been serious with his speed also.