Well one thing is for sure. Fukasaku and Ma toad both knew about Minato. When Jiraiya mentioned that Pain had been one of his students, they both said "You had another pupil."
Jiraiya also never mastered Senjutsu, he just learned to use natural chakra. There's a difference. Jiraiya never fully completed his Sage training. He just got good enough to use it in battle. Also, Fukasaku never said that Jiraiya was the only one that learned Senjutsu. He simply said that it required a large amount of chakra and guts. Two things I'd say Minato Namikaze had, Naruto is his father's son. Another thing is that Jiraiya himself said that Minato had surpassed him. I'm really starting to think that Minato was a Sage.