The discussion about whether or not the Kents should remain dead begs the question and I think it's the crux of the Pre-Crisis/Post-Crisis conflict.
While John Byrne's revamp accomplished a lot of wonderful things for the Superman franchise and brought many new fans to the character that weren't interested in him prior to that, it also seem to divide the fanbase. However, I think the specific details of continuity are less of cause than the issue of how much tragedy should be part of Superman's foundation.
Prior to Byrne, Superman, while generally a cheery hopeful character, also had an underpinning of sadness to him that balanced out his immensely overpowered nature. The Post-Crisis Superman had the same demeanor, but none of tragedy, so his unquestioning belief in hope rings false to many fans because this incarnation of the characters hasn't actually been tested with any real hardships. In other words, it's very easy to be hopeful when you are popular handsome former high school quarterback turned yuppie with two loving parents back home who's secretly the world's greatest superhero.
First and foremost was the fact that Superman's powers couldn't prevent the deaths of the Kents, which transitioned him from boy to man, literally in the Silver Age when it marked the change from Superboy to Superman. By keeping the Kents alive, the Post-Crisis Superman never really learned that lesson. He'd failed to save people on occasion, and would brood about it for a bit, but he never really lost anyone that close to him and, if he ever had any problems, he could always fly back home to Smallville to get a pep talk from Ma & Pa to make him feel better.
There was also the idea that Superman felt a sense of loss about Krypton, which was portrayed as a place of wonder that Kal-El often wished he'd able to save. Byrne's Krypton was quite explicitly a horrible place that deserved to die, that was rejected by Clark in favor of Earth, where he was now born.
The Lois & Clark dynamic Post-Crisis is undeniably better because modern characterization has allowed both of them to be far more 3 dimensional than they were Pre-Crisis. That said, there was also a certain level of sadness to their Pre-Crisis relationship that's gone now, with Clark forever keeping himself apart from the love he most loves.