Gohan's "potential", as far as I consider it, was unlocked fully after Supreme Kai's ritual granted him access to the Mystic state (if you can call it a state...). If he fights, he doesn't need to bother with transformations, and he probably doesn't need to worry about emotional state.... he can use the power, the question is only whether or not he would choose to. I think, after Majin Buu, Gohan might still incrementally increase power proportionate to the fight, but he won't hold back anymore if the fight requires him to.
That being said, Laurcus' comparison of the Godblast to the scope of Gohan's powers does certainly put things into perspective. It doesn't seem like Galactus is actually all that strong a fighter, and that his normal sheer invulnerability to attacks is what lets him get away with.... well, consuming the cosmos. It seems like it takes him a lot of time to do, well, anything... so much time that most of his abilities aren't especially useful in actual combat, especially versus an opponent with speed like Gohan.
Leaning towards Gohan now.