Warning: The following contains spoilers for Thor #17, on sale now from Marvel Comics.
While Odin has worked diligently to keep the peace across the Nine Realms as the King of Asgard and Norse All-Father, he has historically not been a particularly good family man. Repeatedly unfaithful to his wife Freyja and exceedingly cruel to his children, Odin's personal life has been a disaster spanning over a million years and straining his relationships with everyone close to him. Separated from the rest of his family after abdicating the throne of Asgard to Thor following the crossover event War of the Realms, Odin has been uncomfortably thrust back together with his estranged wife and children and finally takes the opportunity to reveal which of his children is his personal favorite.
Since leaving behind Asgard, Odin's marriage to Freyja completely imploded and the two Asgardians separated acrimoniously shortly thereafter. As Thor acclimated to the responsibilities that came with his kingly ascension as the new All-Father, including troubling visions portending the Marvel Universe's prophesied doom, Odin descended into a drunken stupor in a back alley dive bar in the far reaches of the cosmos. And while Odin briefly returned to Asgard to help the kingdom contend with the murderous Donald Blake, he was just quickly cast back out by the embittered Thor. And in Thor #17 by Donny Cates, Michele Bandini, Matthew Wilson and VC's Joe Sabino, Odin finally lets Thor know what he really thinks about him.
Thor and Odin are separately summoned to a remote corner of the Nine Realms in a reunion that was orchestrated by Freyja and Odin's daughter Angela, from the secret tenth realm, Heven. After being attacked by wild beasts, Odin reveals Thor has been his favorite child all along while the God of Thunder feels this praise is far too little far too late as the father and son charge into battle by each other's side. To Thor and Odin's mutual surprise, Angela demands that the two men finally reconcile as the future of Asgard and the wider Marvel Universe has suffered from their perpetual squabbling. If this reconciliation proves impossible, Angela swears she will take Asgard's throne by force, if necessary, to properly lead the kingdom -- an ultimatum that both Thor and Odin act indignantly towards.
And while Odin's passing comment to his son does indeed seem like scant praise, it also holds true, for whatever it's worth, given how poorly Odin treats everyone close to him in his life. As the son of Frost Giants and deeply annoyed by his antics as the God of Mischief, Loki has always been treated by contempt by Odin, with his adoption being more of a political move for the Asgardian to maintain peace with Jotunheim, rather than one primarily driven by paternal love. Angela was straight up banished, along with her entire realm, after Asgard and Heven fell into war, with an enraged Odin keeping her existence a secret for millennia. While the only child of Odin and Freyja, Balder the Brave has always been visibly more insecure in his royal responsibilities, potentially leading Odin to favor Thor.
For all his headstrong pride and stubborn nature and as contentious as their relationship could get, Thor has always been Odin's favored son. Perhaps this connection is because Odin sees so much of himself in the God of Thunder, a distinction that not only fuels their familial love but one that has led Odin to treat his son so harshly at times. And in forcing Thor and Odin to mend fences, Angela is right in sensing that the future of the Marvel Universe depends on their dynamic, with dark things on the horizon as per Thor's visions, hopefully leading for a true reconciliation to take place in the near future.