I wouldn't say that. The supreme being of DC is the writer, as shown in Animal Man for instance (there are others, but Animal Man is a good example).
Id say the Presence should also be above Primal Monitor (even though in an interview, Morrison called it "God" and implied that it's the same thing as the source) only because he's used by a wider variety of writers as being the true "God".
Primal Monitor is a supreme entity featured only in 1 story, kind of like Una in the Warlord series (part of DC), for one.
Should be noted that Warlord did feature a number of powerful beings, it even introduced the abstract Death (in a female form) before Death of the endless was introduced, though she didn't do much.
The most powerful being(s) in the DC universe are the Presence and his evil side the Great Evil Beast, but even the Presence stated that there are forces even beyond his power - he was clearly refering to the writers.
When it comes to Marvel though The One Above All has been established as the most powerful being in that universe, because it is the writer himself, who jumped into the story and proved that he can do whatever he wants to do.
The One Above All from the Marvel universe is actually the most powerful being in all of creation. He might be not the only one, where a writer includes himself in his creation and he most likely also isn't the first one, but the One Above All has the total control over the entire Marvel multiverse, which is a lot bigger than everything else, where the argument could be made that there are other writers in fictions... these writers are not in such a big and rich universe.
With all that being said...
Marvel Universe:
The One Above All
(Pre Retcon Beyonder)
(Pre Retcon Molecule Man)
Thanos with the Heart of the Universe
Scathan the Approver
Protégé
Living Tribunal (who is in my opinion on pair with DC's Presence)
DC Universe:
The Presence / The Great Evil Beast
Michael Demiurgos
Lucifer Morningstar
The Over-Monitor
COIE Spectre (that means no PIS, no jobbing ... just Spectre at his best)
Image Universe:
Miracle Man / Mother Of Existence / Whatever he calls himself
uhm ... Divine Spawn? I'm not buying that one at all :-|