Between Kratos or Nathan Drake.
Sackboy? What's so leading about Sackboy? Ratch n Clank arent even made by Sony and Helghast? I havnt even heard of him/her/it.
I say Kratos. His made by Sony, he has been in a ton of kameos and his not like Drake where he has retired. Kratos has alot more left in his tank. Only downfall with Kratos is his not for the kids so the moscot is clearly aimed for the mature gamers.
Sony OWNS the Ratchet and Clank IP. They have Insomniac handle it, but could pass it to another studio if they saw fit.
Helghast are the antagonist race of the Killzone IP, and have had a presence in the PS brand for a long time.
Sackboy has had a stong presence on all Sony platforms from the PS3 onward, though he has lost steam with LBP3. He has been used often in promoting the PS4 overall though.
Just because you may not be privy to an aspect of Sony IPs does not mean that those options are null. Most people know about them, regardless of your personal perception.