Galactus in his normal state is "middle tier" in terms of godlike beings in the Marvel Universe. (In fact, Galactus dislikes being referred to as a God because he believes that it takes more than just raw power to be considered a deity. It's hard to make a statement of humility sound badass, but Galactus pulls it off.)
"Sphinx! You share the folly of all your lowly species. You believe that power itself makes one a God! But even Galactus, to whom all is possible, even Galactus whose every passing whim becomes reality — even Galactus is no God."
I think it's stated that he's stronger than a Cosmic Cube, but Molecule Man, the Beyonder, and other beings evolved from Cosmic Cubes are equal to or stronger than he is and he's weaker than the Celestials, th Elders f the UNiverse, Cosmic Principals--especially Eternity and Infinity, who are the embodiments of time and space(Eternity also being the anthropomorphic embodiment of th eUniverse. Eternity's Children "Now" and "Then" are the reason why Superheros don't age, time appears to flow weirdly for them, and they can sometimes be in several places at once,) the Living Tribunal(Who is a unique multiversal being who is literally omnipotent but has three personas that must be in agreement before they can act and is basically God's Enforcer) and the One-Above-All is the only being tht is truly omnipotent(One-Above-All is either the Abrahamic God or else, Jack Kirby. He resides at the top of the Marvel Multiverse and all gods in every universe are reflections of himself. OAA has many guises, sees with many eyes, creates with many hands, all of whom are themselves but also Him. His only weapon is Love. He is opposed by the One-Below-All, who likewise has many guises, sees with many eyes, and destroys with many hands who are themselves but lalso him, but unlike the One-Above-All the One-Below-All, who resides in a Hell-Realm at the bottom of the Multiverse, cannot manifest himself outside of one of his avatars. He's been described as "Cosmic Mega Satan" and "God's Hulk.")

Galactus is also an ant compared to Franklin "I literally create Universes for fun" Richards. In fact, Galactus was once Franklin's herald and as a Teenager in Dan Slott's Fantastic Four run, Franklin complains that it was kind of dumb for the adults to leave them behind to stop Doom from screwing things up when Galactus came to Earth and landed in Latveria for exactly that reason(Val complained that she is literally the only person in the world that can successfully reason with Doom and give him criticism that he'll listen too and is, in general, the last person in the world that he would willingly hurt.)

However, Galactus the World Eater is not the True Form of Galactus. Galactus is supposed to be a Lifebringer. A being of infinite power that creates life and holds off Entropy, not a being of ravenous Hungerwho hoars the life force of countless worlds.

In his True Form, Galactus is twice as powerful as he normally is and himself possesses infinite energy. This puts him above the Celestials and most of the Cosmic Principals, but he's still nothing compared to Eternity.

Somewhere in between Eternity and the Living Tribunal comes most versions of the collected Infinity Stones, which make you absolutely Omnipotent but under normal circumstances will only function in their native universe(This does not apply to the MCU versions, which are much weaker and follow different rules but can apparently do whatever the hell they want.)