Comparing deities from different pantheons is like comparing apples and oranges.
The Greek (and especially Norse) gods are intended to seem somewhat like people. They're not to be questioned or countered, but they are bound by fate and seem more like a superpowered, very flawed person than some unstoppable, uncounterable force.
Whereas Marduk, from what I can tell, was intended to be both a metaphor for the conquest of Babylon over other city states and a vessel for the city's ego. They have neither the same intention nor the same philosophy.
In this RPG, with everyone playing under the same ruleset, it's not the best idea to say your character is the most powerful of the gods. The different myths conflict on so many levels that assuming anything that happened in yours is the absolute universe's canon will just lead to conflict. Practice cognitive dissonance, and let the RPG be the proving ground.