Just beause he was the master of the 4th's master doesn't mean he is stronger.like ero said im talking about in his prime not the 62 year old we saw fight orochimaru with barely any of his chakra reserve, we don't know how strong exactly he is since they didn't use any of the filler or flashbacks on showing him fight in the past![]()
but hes still stated as knowing and being able to use all the jutsu in konoha, mastering ninjutsu taijutsu and genjutsu and trained the sannin (so he was minato's master's master).
besides he hand picked minato to be the 4th im sure he knows what hes capable of.
We all know that Naruto is going to be the strongest in the whole mange (we don't actually know it, but it is a fine quess)
(sarutobi was naruto's father's master's master)