I think the reason people care less about the SII death than the one in MoS has to do with tone. Zod's death in SII was a silly, comic-booky thing; it's completely bloodless, and by comic book logic he could totally have survived it (We don't see him hit the bottom of the pit or anything). By contrast, the death scene in MoS (which part I actually
have seen, because spoilers are for wusses

) is much more visceral and brutal, and not nearly as triumphant. If it was something like Supes throwing Zod into the Phantom Zone or something less gruesome, it probably would have gone over better.
Perhaps an improved ending (from a writing standpoint, from what you guys are saying the scene was supposed to accomplish) would maybe be to cut out the family and instead have Supes almost deliver a death blow to Zod...only to pull back and walk away at the last second, showing that he refuses to kill. Zod doesn't accept the surrender and lunges at Supes, but somehow accidentally offs himself in his determination (I don't know, crashes into something or whatnot). Supes doesn't have to kill, Zod's determination is still illustrated, and the threat is still ended.
Or maybe I'm just an idiot.