Who of these (3) three sultans considered the best in Turkey: Sultan Suleiman the Magnificent, Sultan Mehmed the Second, or Sultan Selim the Grim?

Mehmet II the Conqueror is mostly considered as the greatest among them in Turkey. Under his rule, Istanbul flourished as the imperial capital. For centuries, it had been sacked by Latins. By 1204, it had become merely a medieval town and lost its charm and might under the late Eastern Roman emperors, Laskarids and Palaiologs. The city had already lost much of its population before the Turkish conquest. Mehmet II repopulated the city with his subjects with different backgrounds from the Anatolian and Balkan mainland and Aegean islands. This was somewhat unimaginable for most of the other states in the late medieval world.

Mehmet II of Turkey

Mehmet II was a scholar who purportedly spoke at least six languages alongside his native Turkish, including Latin, Arabic, Persian, Greek, and Hebrew. He was deeply interested in contemporary science. He ordered the foundation of the University of Istanbul as a school of theology (medrese) in 1453. He invited Ali Kuşçu, an Eastern Turkic astronomer and mathematician, to continue his studies in Istanbul. Mehmet II was also very fond of arts, especially painting. A Renaissance-era Italian painter, Gentile Bellini, visited his court and painted at least one portrait of him in 1480. Mehmet II was a general and a professional soldier who also had engineering skills. He led the team which was responsible for the task of designing cannons (great Turkish bombards) for his army

Mehmet II and Ali Kuşçu, the Eastern Turkic astronomer and mathematician

Under his reign, the Turkish Empire became a European and Mediterranean power of the 15th century. His efforts constituted the mere basis of the conquests and achievements of his grandson Selim I the Grim and his great-grandson Süleyman I the Magnificent.
His published acts defined the traditional Turkish law. His Code of the Conqueror (Fatih Kanunnamesi) formed the judicial basis of the decisions of the emperors after him. For most historians who studied the period encompassing his reign, Mehmet II was considered to be a just and fair ruler who granted religious freedom to all his subjects. He protected Islam and his Turkish & other Muslim subjects against any foreign aggression. The Emperor also helped the Orthodox patriarchate in Istanbul to flourish again within the borders of Eastern Roman Christianity and also declared a “ferman” (ie. decree) to protect the rights of the Bosnian Franciscans.

Mehmet II’s accession to the throne

An artwork depicting Mehmet II of Turkey and Gennadius, then Orthodox patriarch of Istanbul

Mehmet II’s decree granting freedom to the Franciscans in Bosnia

Mehmet II the Conqueror was the only Turkish emperor whose portrait was featured on a Republican Turkish banknote. The founder of the Turkish Republic and its first president, Mustafa Kemal Atatürk also admired Mehmet II’s achievements and spoke very highly of him. His name became a popular given name as Fatih Mehmet or Mehmet Fatih (with the title Fatih meaning “conqueror”) in Turkey, including mine, as you have already noticed.

Reverse of the 1000 Turkish Lira from the 1980s featuring Mehmet II the Conqueror, the obverse featured Atatürk as usual

Conclusion

Mehmet II’s impact on Turkish history and culture of today is far more important compared to Selim’s and Süleyman’s.