It depends where the fight is.
A hungry Galactus have statlemated Agamatto in a place where he was all powerful and can't die.
On another fight, Galactus owned Mephisto by threaten him to feed on hell.
In both fight, I don't think that Agamatto and Mephisto could have possibly get even 1 from Galactus if the fights had occured in, let say, space.
I don't know for this fight, since they are 4, but I wouldn't count Galactus out.