I think the way Madara and Kaido are perceived is good, and both authors have made it clear that both characters are fearsome. However, I don't think that this is an argument that will lead anywhere. Madara was indeed fearsome, right, we know that, but that didn't stop random people from attacking him. Do we expect characters to retreat or go back home out of fear of Madara instead of facing him? At least Kaido spent 20 years in Wano frightening external enemies, as Green Bull and Kinemon reported, and was recognized by Blackbeard as a fearsome monster, etc.
The real question lies in the following question: why were they feared? I think both authors have made it clear enough that the fear of others was not unfounded.
However, Kaido was much more wicked than Madara. If you lose to him, your fate is sealed; often, you would prefer death over working as a slave for Kaido for the rest of your life. Madara's plans for the world weren't that bad; however, Kaido longed for the destruction of the world itself. The Moon Eye Plan wasn't so bad for people, a world without war and crime, the complete opposite of what Kaido desired, which was to plunge the world into chaos.
Madara's personality? Damn, that's awful. I can't imagine anyone wanting to go have a drink with him or anything like Sasaki wanted to do with Kaido. Kaido had subordinates who respected him, were willing to work for him to achieve his goals, and were willing to sacrifice themselves for him, like King, for example. Madara, on the other hand, captivated others through his plan; I don't think Madara had anyone willing to sacrifice themselves for him.
Taking a closer look, Madara is terrible and Kaido is much better. There's also the fact that Kaido has a daughter, which adds more depth to his character. Did Madara ever even touch a woman in his life, to be honest?