What, a thread on bad Supermans has gotten 20+ responses...and not ONE of them have mentioned SUPERMAN III and SUPERMAN IV? Shame!

There have been some pretty lousy versions of Superman, but I don't think there's ever been a single version of the character completely devoid of at least ONE good idea.
As lousy as LOIS AND CLARK was (and it was pretty bad...George Jefferson as the Toyman? Yeesh!) it had one interesting idea: it made Ma Kent a jeans n' t-shirt wearing, hip old lady, the kind that would do Tai Chi and occasionally skydive. She was much more vivacious and fun than the pie-baking stereotype/nonentity she was in so many other mediums, including the comics.
Mostly, LOIS AND CLARK offended me because it was a comedy, and it wasn't very funny.
My least favorite Superman ever was the rough 1960s Superman/Aquaman Hour. In KAVALIER AND CLAY, the creators of the Escapist had the indignity of their character entering another medium badly. They described all the characters behaving as if they were "slightly mentally retarded."
I laughed so hard at that, because I know what they mean. There was something dimwitted about Superman in "Superman/Aquaman."
The worst version of Superman is one that never saw the light of day (but has been much discussed): Tim Burton's aborted movie incarnation (black-clad, flightless, etc). As for the comics, Electric Superman is the worst.
Quoted for truth!
Somehow, Burton's version didn't horrify me quite so much as the insanely awful script that Keith Giffen wrote, which was Superman vs. Lobo as a "comedy." Giffen + "Comedy" = Destruction of Sanity.