John Byrne has been very explicit that he wishes that he'd been allowed to make the changes he wanted to make within the established continuity, without a reboot. I think most of it wouldn't have been very hard. Close down the Fortress, kill all the Phantom Zone villains, have Luthor become a supposedly legit businessman, get rid of "Clark Kent, anchorman," have Lana (not Lois) learn that Clark and Superman are the same guy, destroy all non-green Kryptonite, have some Big Cosmic Thing happen so Superman can't fly even near lightspeed anymore, let alone travel forward and backward through time under his own power...
There could've even been some minor retcons -- nobody knew that Superboy lived in Smallville except the Kents, Brainiac destroyed Kandor instead of shrinking it (OK, that's kind of major), the Kents died in some normal way than through "a fatal and rare tropical disease." (Drunk driver, maybe?)
This would've been far less divisive than THE MAN OF STEEL. I think it would've been better, even though there are parts of MOS that I very much like.