I think he's being sarcastic. Either that, or he's so young that Duke Nukem was well before his time, and he somehow hasn't come across it in his internet travels yet.
I usually am not into trying out different games, and tend to stick only with the ones I have played or have been recommended. By the way, just because I say he looks like Sarge from Quake 3 doesn't actually mean I don't know Duke Nukem; not saying that I actually know it, but if someone sees a similarity between Picture A and Character from Game B, he might state it, and this doesn't mean he doesn't know of the game behind Picture A.
Anyways, yeah, I'm not into collecting games. Our generation sells off Metal Gear, Counter Strike, Tiberium Wars, etc., etc., etc., but I tend to stick on the older games, namely Populous: The Beginning, the AOE series, AOM, Quake 3, and of course, FreeSpace.
...oh wait, so Duke Nukem was released in 1996? I never knowww....