Think about it. Ezio is from a rich family and so was Bruce. Their family are killed (almost in AC2). They both go through a personal rite of passage, Ezio becomes an assassin and Bruce becomes Batman. They also have gadgets Batman has the Baterang and Ezio has the hidden blades. They both have distinctive costumes. They fight for vengeance. They scale the city heights to move through it. They are skilled at CQC combat. They have a close personal friend that helps them no matter what (Alfred and Leonado).