Who has priority in leading the congregational prayer (Imamah) in the mosque: the one who has memorized the most of the Quran, or the best reciter among them, or the most knowledgeable of Islamic rulings, or the most consistent in attending congregational prayers?

The most deserving of leading the prayer is the one most knowledgeable of the Book of Allah—that is, the one who has memorized the most—provided he knows the rulings of prayer and is free from فسق (open transgression). However, if he is a فاسق (transgressor), then someone lesser in recitation should be given precedence over him if that person is pious and observant of his prayers in congregation.