I know I'm hugely in the minority here but I've always felt it is the job of later writers and stories to maintain continuity with what has already been established. I'm not talking about every little detail of every story but the big things.
I would like to see DC do what Marvel did until recently: the entire history happened. Maybe it happened more recently and we have to squint our brains a lot and imagine there were differences because something from 1961 now happened in 2008. Or just don't update and explain it. Just say it happened. Let's say I never read Iron-Man before but I read the latest issue and want to know the history. So I go back and read the first appearance. Okay maybe Vietnam is now Iraq but the story still basically happened. The stories all happened. Maybe the Cold War with Russia is now Hydra. Or maybe let's just not explain it. It's Iron-Man's history and it happened.
What I hate with DC is I can't do that. The Nu Superman was a good attempt to recreate the Golden Age Superman. In a way, what I'd prefer to see restored is whatever was the original continuity. Albeit you can explain that some things you thought you saw wasn't what really happened. Let's face it. Over at Marvel, the greatest retcon in history was Captain America being frozen and reawakening later- and it just got better and better the further from his time the reawakening occurred.
But just in general:
Superman being the first super hero. Whether this is done by having him debut in 1938 or by throwing out all the World War II stuff and no super beings show up until Superman debuts.
To maintain continuity, the Kents should die before he becomes Superman BUT this is comic books. They can always be brought back.
The Kents should be running the General store. In fact, holy mundania, Batman. There could be a story about how they are being put out of business by the rise of the huge National companies like Wal-Mart.
Superman having been Superboy is not the original continuity, of course. Though there are rich stories there. To this day, when someone says, "Superboy", it means, "The adventures of Superman when he was a boy" then reality sinks in and I realize they are talking about Kon-El or someone.
At any rate, I'm just ranting as I realize this stuff isn't likely to happen.