I Seaguy and Gerber's defenders and dislike Morrison's more mainstream work, in which it seems to me that he caters to the worst of readers' wish-fulfillment fantasies.
Seaguy OTOH I see as an inventive examination of the basic elements of the hero's story (i.e. any hero's story), as well as what might be described as a Gerberesque indictment of how the powers-that-be attempt to control that story for their own ends.
I'd pick Secret Wars as a representative "Classic comic I hate". Not only is it a flimsy - to the point of near non-existence - story idea in itself, but it was also a precursor to the many similarly weak stories (or "events") we continue to see in mainstream superhero comics right to this day.