These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Awesome Ego: Duke is a self-centered, politically incorrect chauvinist bastard. And the fans love him for it, both in and out of universe.
Duke Nukem II explicitly says that he's so vain that he likes to collect his own memorabilia (which is a primary source of points in the game.)
Crowning Moment of Awesome: In Land of Babes, despite being non-canon, at some point Duke is repopulating Earth, by having almost non-stop sex with all females that remained after all males were killed.