Shaykhul Islaam Ibn Taymiyyah (may Allaah have mercy upon him said): "They (Ahlus Sunnah Wal-Jamaa'ah) accept what has been reported continuously from the Prince of the Believers, 'Ali Ibn Abi Talib (may Allah be pleased with him), and from others, that the best men of this 'Ummah after its Prophet are: Abu Bakr; then 'Umar; third, 'Uthman, and fourth, 'Ali Ibn Abi Talib (may Allah be pleased with them all). All Traditions have indicated, and all Sahabah (may Allah be pleased with them all) have agreed upon giving priority to 'Uthman out of regard for his allegiance (al-Bai'ah), although some of the people of the Sunnah are disputing over whether 'Uthman or 'Ali (may Allah be pleased with both of them) has the priority, after they (the people of the Sunnah) had agreed upon giving priority to Abu Bakr and 'Umar. Some people gave the priority to 'Uthman and kept silent and considered 'Ali to be the fourth. However, some people preferred 'Ali. And some remained neutral. But the people of the Sunnah settled on preferring 'Uthman, even though this matter - the matter of 'Uthman and 'Ali - is not of the fundamentals. The majority of the people of the Sunnah do not consider disagreeing in this matter as being misled. Rather, it is in the matter of the "Question of the Caliphate" where they consider the disagreeing person to be misled.
Ahl as-Sunnah believe that the Caliph after the Messenger of Allah (peace be upon him) is Abu Bakr; then 'Umar; then 'Uthman, then 'Ali, and that whoever contests the Caliphate of any one of these Imams is indeed more lost than an ass." ('Aqeedatul-Waasitiyyah)
The Messenger of Allaah (صلى الله عليه وسلم) remarked to Hadrat Ali (رضي الله عنه), "You are to me like Haroon (عليه السلام) was to Moosa (عليه السلام), except that there is to be no prophet after me." His lineage is: 'Ali son of Abu Talib son of 'Abdul-Muttalib son of Hashim son of 'Abd Manaf son of Qusayy al-Qurashi.