It's not that difficult to depict who would win in a fight between madara and saitama. Saitama has incredible strength and could easily beat madara in hand to hand combat. But you're failing to take one thing into account, genjutsu. Assuming saitama is and can be affected by genjutsu, then there's no doubt madara would win. Any genjutsu, maybe even one as weak as kurenai's could end saitama, since he doesn't have any powers, and just raw strength.
