Someone asks if great leaders of other faiths could have been prophets?

Given that Allah says in the Quran, “And for every nation there is a messenger.” (10:47), we must keep an open mind that this is a possibility. While some of the teachings of Buddha are not in line with the Islamic faith, it could be said that the message was changed or evolved as time passed.

Allah will not punish a nation while they did not receive the message of Islam. And Allah knows best who these Messengers were.