Mogo's got what? Two feats?
Granted, one of them is curbstomping a pretty large portion of the Black Lantern Corp but still, we haven't seen enough from him to truely determine his power level, let alone know if he could take someone as powerful as Galactus.
To rephrase, I don't believe we've seen anything that would lead us to believe Mogo can beat Galactus.
I just don't particularly think a character with very few showings can be used very well in battles. You've obviously got omnipotents that are far above him and anything less than a GL is obviously far below him but that leaves a pretty dang big power gap that Mogo falls into somewhere. Galactus is on the high end so Mogo probably can't beat him but it's just the principle of not saying "Galactus wins" if you don't really know and I don't see how we could really know.
@Zoom: Um... Mogo defeated the entire Sinestro Corps and created armies of superhuman flying brick constructs.... while holding back so as to NOT kill .... while in hibernation..... Yeah. That's how monstrous he is when he's basically sleeping. Imagine if he's awake.
Mogo is a real beast.
Think of Galactus as a hunter with a gun.
Think of most planets as lions
Think of Mogo as a lion with steel plate armor with kevlar over it.... and a laser beam strapped to its head.
Sure, Galactus -could- win. MAYBE. But I wouldnt count on it. If Ego's ever given Galactus even the slightest bit of trouble at ALL, Mogo would at least send Galactus into a tactical retreat until he can figure a way to feast on him in a way which wouldnt be a pyrrhic victory at best.