I'm a bit on the other side of the fence. I don't mind temporary tweaks to characters, because I do like to see some variety even with established characters. But it needs to be temporary, especially where personalities and values core to the character are concerned.
But that's in the comics. In the movies, which are much more mass market and heavily exposed, we really ought to be seeing something pretty close to the "standard" portrayal of a character, because that's going to be the baseline for the character for way more people. Odds are, someone who barely knows anything about Superman probably expects to see the optimistic, moral, goody-two-shoes guy. If you instead show a movie about an omnipotent, brooding alien loner, then 1) that might turn them off and 2) it doesn't tie in to the comics very well.