Part1 Jiraya
Shounensuki said:
「四代目と比べられりゃ 誰だってキツイだろうーよ なんせ あやつは忍としての器は歴代一だ った… 術の才に溢れ 頭脳明晰…人望に満ち まぁ…ワシ並みに男前だったしのォ」
"Being compared to the Yondaime would be hard for anyone. Anyhow, that guy's ability as a shinobi was first among all... There was no end to his ability with jutsu. He had a keen mind... Very popular. Well... he was a handsome man, like me."
Part1 Tsunade
"But he died too early..."
Part2 Jiraya
"Minato was a rare genius, we've not seen someone like him in a while"
Part2 Jiraya(against Pain)
"He wasn't someone who would do something without a reason"
"He(Minato) is the savior of the world"
War arc Tsunade
"I knew he wasn't a man who would do something without a reason"
War arc Ay(Raikage)
"He was a man that I thought no shinobi would surpass"
"Even with so much power(Minato's power), he died because he underestimated the power of the Kyubi" Basically for Ay, Minato's power was so incredible he didn't think he could lose to Kyubi
"The savior(Minato) still lives inside you(Naruto)
War arc Minato
- Save entire shinobis 2 times
- Save the 2 main characters a few times
- Create a plan on the spot we shinobis he met a second or 2 ago
- Weaken Jubidara's defense armless to support Gai with that plan
Hagomoro
"Children(Naruto) don't always born with their parents(Minato and Kushina) full potential"
Basically Minato had more potential than Naruto
Nothing was a retcon. Minato was simply portrayed as the shinobi with the most potential. He mastered complicated techniques easily, creating some and was still in process to master others before dying(completing rasengan, mastering Sage Mode and so on). All that was to show if Minato lived a little longer, he could have been the strongest shinobi in history. It's basically how he he has been portrayed