Why is Toyotomi Hideyoshi more commonly regarded as one of Japan's greatest men as opposed to Oda Nobunaga of Tokugawa Ieyasu?

All three are well regarded. People have their favorites based on their personalities and on what they did.

There are two popular ditties that encapsulate the three unifiers. First set describes their personalities.

Nobunaga: If the cuckoo won't sing, then kill it. "Nakanu nara, koroshite shimae, hototogisu."

Hideyoshi: If the cuckoo won't sing, I'll make it sing. "Nakanu nara, nakasete miyou, hototogisu."

Ieyasu: If the cuckoo won't sing, I'll wait for it to sing. "Nakanu nara, nakumade matou, hototogisu."

The second one describes what they did.

Oda pounds, then Hashiba (Toyotomi) kneads the rice cake of the realm. Tokugawa sits and eats it. "Oda ga tsuki, Hashiba ga koneshi, tenkamochi. Suwarishimama ni kurau wa Tokugawa."

So Nobunaga did the hardest work, Hideyoshi also put in a lot of effort but Ieyasu enjoyed the fruits of their labor.