Why do people believe 2pac is the greatest rapper ever?

i do respect him! i think he is a hall of fame legend! but i dnt even think he's top 5! i mean i know he rapped about real ****! but as far as his lyrics go, i jus think their are soo manny other rappers dat could lyraclly crush him! and i think biggie was even by far better!(though no the greatest!) i personally think NAS is the greatest!(and im a dirty south texan saying dis sh!t.) but das not the point! my point is that jus couse he might have been the greatest back den, people cnt accept that he's not any more!im not trying to crush pac couse i do respect him! but their are many that are lyraclly better and here are a some of dem ........NAS, jadakiss, cidy, lupe f, jay z, kanye, the clipse, wayne, chamillioniare!!!!!!!!!