Not a chance, people talk trash or talk well of people all the time and it hardly ever is the case. If you listened to whatever the manga characters said then stuff we have seen would just be ridiculous. According to Ten-ten, Neji is unbeatable. Iruka was the one who said that the third was the strongest, is he the most reliable source? Characters in the manga say things all the time that contradict each other.
Now that I have answered the thread question I am going to attack the characters statements, not yours but the characters in the manga.
I don't know if you believe that Sakumo is stronger than the Sannin but no one said that in the manga, in the manga Minato said, and this is a direct quote you can check the chapters if you don't believe me, "His name had respect on the same level as the legendary Sannin", respect and power are different. All the kages have about equal levels of respect but some are much stronger than others.
Now about the third, I know Hiruzen was strong but strongest Hokage? Even in his prime I highly doubt that. It would be tough to rank the Hokages as Konoha's kages have all been super boss (other than Tsunade who is just alright). Saying that for me strongest Kage would have to go to Minato followed by hashirama and then Tobirama/Hiruzen and finally Tsunade.