There's nothing better than comparing two entirely different superheroes or supervillains from two entirely different universes. It's something fans of the DC and the Marvel Comics do very frequently to understand who is stronger and why.
It's now time to compare Galactus, one of Marvel's strongest ever supervillains, to the DC Universe. While Galactus has a lot of diversity in his superpowers (celestial being, telepathic, telekinetic, etc), unsurprisingly, some superheroes in the DC Comics are capable of not only doing what he does but better. It's important to remember that only power levels and the individual superpowers are being compared and not what would happen if they face each other in battle.
10 Orion
Orion, the son of Darkseid, is undoubtedly a strong celestial being capable of everything that his father can do. There is a basic character difference here, though, and that is Orion being a good guy and wanting to take on his father, Darkseid, and the evil that he has spread. Orion defeated Darkseid as well and that's no mean feat. Orion is telepathic, telekinetic, and has the means to use the Omega Beam; a weapon that can be used to erase anyone from existence. Galactus can't compete with this.
9 Captain Atom
What to say about Captain Atom himself, who has the means to use unlimited cosmic energy all the while tweaking with the quantum world? Nathaniel Adam is Captain Atom's real name and as everyone would have guessed by now, he gained his superpowers due to an experiment gone wrong. Captain Atom is practically immortal, can manipulate quantum fields, and can play with reality just the way he wants to. It's incredible the stuff he can do and the things he can survive.
8 Phantom Stranger
While having limited appearances in the DC Universe, the Phantom Stranger has made sure to leave the maximum impact. Phantom Stranger is a magician, time-traveller, loves to teleport himself, and is immortal. If that's not enough, he is said to have a bottomless pit of superpowers.
On top of that, he can travel between dimensions like he is going through doors of different rooms. This DC superhero has never used his superpowers to the full extent as his position in the DC Universe has been that to guide the others around him.
7 The Endless
A dysfunctional family that embodies everything in the DC Universe, The Endless are beings who define existence. A group of seven siblings namely Death, Destiny, Dream, Desire, Destruction, Despair, and Delirium, The Endless don't know the kind of powers vested in them. Together or one at a time, they can drive anyone crazy in the DC Universe. Galactus can be killed by Death, destroyed by Destiny, trapped by Dream, etc, and the list goes on and on.
6 The Guardians Of The Universe
The Guardians of the Universe or Oa are somewhat very old and ancient. They are a group of cosmic beings who were able to use the power of the emotional spectrum and are the founding members of the Green Lantern Corps. Their combined strength is unlimited and even though Galactus might have a case against one of them, together, they are simply unstoppable. Galactus might be in a better position to join them, instead of going against them.
5 The Spectre
The Spectre was given birth by The Presence and that alone should qualify him as one of the strongest beings or spirits to ever exist in the DC Universe. Spectre needs a human host to function and once that hurdle is crossed, he has near-unlimited superpowers in his grasp. He can do anything he imagines, quite literally, and so far, it has included manipulating reality, time control, playing with his enemy's mind, and destroying universes, among numerous other things.
4 Lucifer Morningstar
Lucifer is the living and breathing son of God, who is nigh-omnipotent, meaning he has holy powers that allow him to do the unthinkable. He is immortal, capable of playing with mortals' minds, can project energy, play with matter, and do magical spells.
Lucifer's presence in the DC Universe cannot be ignored and his superpowers come close to The Presence. The most intriguing superpower he has at his disposal is pyrokinesis or the ability to use the energy of the Suns he has birthed.
3 Michael Demiurgos
Michael Demiurgos is Lucifer's brother and an Archangel capable of doing everything the Devil from Hell can do and much more. He too is telepathic, telekinetic, immortal, and all other things. Michael led the rebellion for the side of Heaven against Lucifer. This storyline led to the birth of another one of DC's strongest beings, Ellaine Belloc. Michael is said to be stronger than Lucifer due to him being a bit purer than his brother. It's not a surprise. Galactus can only wish he trumped an angel when it comes to superpowers.
2 Doctor Manhattan
Jonathan Osterman is another human who fell prey to an experiment gone wrong. His body was disintegrated and he became Doctor Manhattan; an all-powerful being capable of doing anything. He has all the superpowers one can think of: telepathy, telekinesis, body size alteration, time travel, matter manipulation, reconstruction, immortality, etc. And that's not even half of it; he can do much more and that makes him one scary DC superhero.
1 The Presence
The Presence is basically DC's answer to God. The one who knows all about the multiverse everyone resides in and the one who is responsible for leaving angels and demons in their respective places. Again, The Presence has not shown up many times and his powers are still unknown to an extent but one thing is for sure, he is the strongest being in DC Comics. Galactus can only bow down to him because he is the equivalent to One-Above-All from the Marvel Universe.