WARNING: Spoilers follow for Fantastic Four: Antithesis #4 by Mark Waid, Neal Adams, Mark Farmer, Laura Martin, and VC's Joe Caramagna, on sale now.
In the recent series Fantastic Four: Antithesis, Marvel told a flashback story where Galactus came to the Fantastic Four for their help. It resulted in Reed Richards taking the power of Galactus, with the thought of finally stopping their threat for good.
However, the Fantastic Four wouldn't let Reed take his own life, and they set out to find a way to get in touch with him again. They found Agatha Harkness and asked her to use her powers in conjunction with Silver Surfer's Power Cosmic to reach Reed. However, Surfer needed something to bring Richards back, and the FF helped him figure it out.
The Thing mentioned that the best way to lure Reed back to Earth was to remind him why they are so "tasty." Sue looked to Silver Surfer and asked him what it was about the Earth that caused him to believe it needed to be saved in the first place. She asked him to think back to the day where he turned against Galactus and saved the Earth and asked him why he did it. Silver Surfer looked back and said there was something "unique" about Earth when it came to its place in the cosmos, and he explained the difference between the citizens of Earth compared to other planets and worlds.
Silver Surfer said that the Earth was vibrant with a life force that had nothing to do with its size or natural resources, which Galactus feeds on. Instead, he recognized an "unmatched spirit" when it came to humans on Earth. He pointed out the people of Earth are capable of the worst, from war to injustice and prejudice. However, while these are all "learned attitudes, learned behaviors," the people of Earth are good at heart. Silver Surfer called Earthlings the kindest. While Skrulls use savagery to conquer, and the Kree use cruelty to lead, humans use their compassion to achieve greatness.
"The Saga of Galactus" took place in Fantastic Four #48-50 by Stan Lee, Jack Kirby, Joe Sinnott, and S. Rosen, when Silver Surfer led Galactus to Earth and the Eater of Worlds prepared to consume the planet. In issue #50, Silver Surfer turned on his master and betrayed Galactus when he realized Earth was worth saving. When Galactus said the humans were ants in an anthill and meant nothing, Surfer said he finally found something worth fighting for. He attacked Galactus. When Galactus seemed shocked that Surfer betrayed him, his herald said he found his conscience again on Earth.
Now, with Reed Richards holding the Power Cosmic, it was up to the Silver Surfer to show him what was so rich about Earth, and the hunger growing in him forced him to return to the planet. At this time, his friends and family were able to talk him down and convince him to give the powers back to Galan and return to his role as Mister Fantastic, a hero of Earth. However, Silver Surfer's memories reminding him of the goodness in the hearts of humanity, Reed left Galactus with a bit of consciousness as well, similar to what made the Silver Surfer come to love Earth.