This. He is a new version of Agassi and like Agassi he should reach 8 majors. He needs three more majors to be considered one of the greats. Of particular importance is winning the French open at least once.
I personaly feel Djokovic is greater than Agassi mostly because he is such a mental giant, almost unlike anything I have ever seen on the mental department, if you take into consideration the endurance and long battle style he got. Sampras was amazing in finding the right shot at the right time when under pressure but Djokovic got the combination of endurance and mental strength which is simply exceptional.