I thought Drake might be. He appeals pretty well to a large variety of people, even to my family friends who are around 10 years old. Kratos just has this whole "die-world-die" thing going on that makes me think he couldn't be the face.
This is for everyone different. There can't be a true face. Lots of people would say Kratos and Many others would say Sweet Tooth or Nathan Drake. It's just what game you like the most if you like destroying cars it's obvious Sweet Tooth is in your eyes the true face of sony. As for third person shooter lovers it is obviously Nathan Drake.
All of Sony's characters are equal... but if one had to be the "face" of Sony, I would say Nathan Drake.
Cole Macgrath would be a fitting Sony mascot. He has electric powers, he's a badass, and just look at him. He simply just looks like Sony's mascot (His appearance and attitude.) But he's no where near as popular as Kratos and Drake.
In the Michael commercial, when the bartender is saluting Michael (aka us), he looks at Kratos for approval in putting his portrait in the ceiling. Clearly Kratos is bossing the Sony tavern.