Well, in most cases, and in my personal opinion, the more formal '______of ______' seems more epic than '_______'s ______'.
Which do you think sounds better? 'The Melancholy of Haruhi Suzumiya' or 'Haruhi Suzumiya's Melancholy'? It would translate either way from 'Suzumiya Haruhi no Yuutsu'. It's all a matter of preference and what sounds better.
However, what I think AK's trying to say is 'Roto13 is an idiot', which would be 'Roto13 wa baka' (or is it 'Roto13 ga baka'? I always get the two particles confused), not 'Roto13 no baka'.