Answer 1
Currently Imam Khamenei is leader of Shia Muslims.
Answer 2
Islam is not like Catholicism where all Muslims are ruled by one worldwide leader (Pope). Even among the Shia, Imam Khamenei is first among equals (the community of Ayatollah) and his religious opinions can be rejected by other Imams. Islam functions much more like Judaism or Protestantism where there is no leader of the worldwide movement, but different leaders in different countries who are respected for their religious acumen.
THE BEST ONE IS ALLAH
And this are the oters that he made to lead too but still he is THE BEST ONE. The Holy Quran , Angals (Jibreel) , Proret Muhammed (P.B.U.H).
Answer-2
The holy Prophet Hazrat Muhammad Sallal la ho wasallam.
Muslims do not have one leader, like a pope. There are many many scholars who are well-respected by most Muslims, though.
Allah is the spiritual leader of muslims.
A kafir can not lead Muslims. Only a Muslim can lead Muslims.
Saladin led the Muslims in some of the Crusades.
I'm not Muslim but I think their leader is Mohammed.
Jesus
Ali
saladin
Agakhan is leader of Ismaili muslims.
Iman is not a religios leader. Iman is what Muslims call their faith.
An Imam
Imam, sheikh, Ayatuallah, ....