Picard single-handedly saved the Federation, the Klingon Empire, and
all of humanity while still a lowly captain.
Picard did some amazing things. He saved the Federation, he helped the Klingon empire and he basically saved humanity all while just a captain. Yeah, Captain Kirk did some amazing things but he was also an admiral and a whole bunch of other titles by the end of it all.
Picard remained a captain through it all and proved why that title should mean something. Captain Jean-Luc Picard doesn’t let his title stop him from doing what is right and it makes him the better captain easily. Kirk, while he still does things that are very much above his rank, usually wants the title. And then when he gets that new title, he likes it for a little while and then doesn’t anymore.
He gets admiral and then wants to be a captain again because he misses being on the ship. But Picard knows where he is meant to be and stays there because he knows his duties. He saved a whole planet (with Kirk at his side) because it was just the right thing to do and that is what he, as a captain, is meant to do.
Picard looks out for the people and that is why he is a great man.