After years of crap, no talent... i gotta say its has to be the heavyweight divy. Its become very compelling and lot of possible scenarios, and very exciting right now. With all the new very talented heavyweights making big splashes in the last year or so, how can we not say the heavyweight division is at the top.
Funny how things change, it used to be the light heavyweight division for a long time when Chuck/Tito/Couture then it was the welterweight with GSP/Penn/Hughes and so on...