Ego without the Novaforce he currently possesses would probably beat Mogo. Not easily. But with the array of powers he possessed, I definitely think he would. Although both Mogo and Ego have shown weaknesses to little people running around in their biospheres and trying to sabotage them from within, that isn't the case here. But I haven't seen a whole bunch of feats from Mogo to be able to make a guess at the wins/losses split...