A 'ruler' does not become 'greatest' or 'great' by simply winning battles, he has to rule the people good enough. The combination is hardly seen in any ruler here in the list.
So, my question is, where is the option 'Muhammad (pbuh)'?
Here are few notable instances of his life:
1. He cancelled the slavery system from the Arabs.
2. He removed the racism and differences between black and white people.
3. He lead a normal life. His wife Khadiza (R) gave her all her wealth but he spent all of them for the poor. He had only a mat to sleep on the floor.
4. His beloved daughter asked him for a maid to help her in her household work as he was in charge of distributing wealth from government account. He refused to do so instead told her to be patient.
5. He was victorious in all of his battles. In the Battle of Badr, 313 Muslims faced 1000 men of Quraish who were even far superior in terms of weapons, and defeated the Quraish. In the Battle of Uhud, 700 Muslims faced 3000 Quraish’s soldiers and the result remained draw. In Battle of Ahzab, Prophet’s 3,000 men defended Madinah against allied forces of 10,000 strong and forced the allies to withdraw their siege of the city. In the Battle of Khaibar, Prophet conquered the Jews with a force of only 1400 men while the Jews living in the strong forts of Khaibar were no less than 10,000. In the Battle of Mutah, the Prophet sent 3000 Muslims who successfully faced professionally trained and well-equipped army of 100,000 of the ruler of Ghussan. In the last year of his campaigns, Muhammad (PBUH) marched against Rome with a force of 30,000 while the Romans had organised a force of over 100,000 strong on the borders of the infant Islamic state.
6. He was a believer of peace. During his early prophethood, people of Mecca abused him and mocked and tortured him and his followers. Even he was forced to leave Mecca to Medinah for saving his life. But when he conquered Mecca after few years, he pronounced 'forgiveness' for all.
7. He introduced the system of 'Jakat' for the poor people where a Muslim with certain amount of wealth had to pay it. The rate was 2.5%. 'Jakat' was gathered in the 'baitul maal' (treasury in islamic state) and distributed among the poor. In spite of having lots of wealth in his control, he lead a very poor life wearing torn clothes and eating inexpensive foods.
8. Even though he was a leader, he worked with the muslims. In the battle of 'trench' when Muslims were digging trench around Medinah to defend themselves from the attack of the Non-muslims, everyone was working including the ruler Muhammad pbuh. Few companions of him came and complained that they did not have food from yesterday. Muhammad pbuh smiled and removed his shirt to show a stone tied with his belly. He said, I did not have any food from last 3 days.
9. He treated Muslims and Non-muslims equally. He prohibited the destruction of non-muslim prayer places.
In spite of these great achievements, he is not mentioned by some historians that much. I read his life story and I can say he was the best ruler of his time.
