I don't think people avoided ST:ID - after all it's the most successful Trek movie ever made! I think that the marketing was too downbeat though and if it had been promoted as more of an Indiana Jones style romp then I think it'd have made more money.
Superman's success is likely due to the excellent first film starring Christopher Reeve. Everyone wants the next S-man film to be that good! I also think that pretty much everyone has forgotten Superman Returns, so there weren't the skeptics that there were for say the amazing Spiderman reboot.
For what it's worth, I thought Superman was terrible, if you're interested, here are my reviews of ST:ID and MOS: