This is a pretty good debate.
Alen is probably one of the top two historians on the forum, along with Seven, Martin is pretty knowledgeable in science but mostly with computer science, but I honestly don't know Osman apart from football. While the Somali-Swede knows football like the back of his hand, I don't really see him partaking in other topics besides current events, so it's hard to say.
Deneb knows his history, knows current events, has quite a lot of culture behind him, and knows more about the most important topic facing the West in today's world than anybody else here -- the global economy. Clearly the guy knows quite a lot about most topics discussed here, so it's no contest, IMO.