I thought the Doomsday fight was ok, but they had major flaws. The main one being that Superman got Doomsday into space, instead of pushing him into space and letting him drift, Superman returned him to Earth. In the comics he tried to carry Doomsday into space to get rid of him, but Doomsday kicked himself free and the fight continued on the ground.
The mourning was way too short. It was 5 maybe 10 minutes max. Not enough time to really feel his passing.
Finally, and this is the biggest flaw, the fake Superman was crap. Having the Cyborg and Eradicator as potential Superman added mystery to it. Either could be Superman. This clone was just presumed to be Superman right off the bat and they didn't have any mystery as to who or what he was.
