Pity Brandon Routh, the actor plucked from obscurity, liberally greased up, and squeezed into… Read…
By all accounts, Brandon Routh has an enormous penis, yet it's Henry Cavill who looks like he's about to burst out of his tights. Somehow, the all-blue of the outfit draws the eye right to the crotch, while the red briefs allow the eye to pass over it unmolested. Look, I'm not saying there's anything wrong with thinking about Superman's penis - far from it - I just think it should be a matter of choice and not necessity.
(And please don't talk to me about "armor," in either comics or live-action. If it's skin-tight armor that shows the contours of muscles, it's skin-tight. That's the operative part. A dude could be wearing a skin-tight mattress, but if it's skin-tight, it's skin-tight.)
Old-time-y circus strongmen weren't idiots - they knew putting their underwear on the outside proved that they were wearing underwear, and allowed them to reveal the rest of their bodies safely in a modest era. When designing Superman, Siegel and Shuster may have chosen that aspect of the strongman's costumes inadvertently (although I sincerely doubt it) but it helped perform the same function, and furthermore, became an integral part of the visual identity of the superhero genre.
By taking away Superman's briefs in both the comics and the movies, DC is working against 80 years of tradition, a tradition that superheroes have completely claimed from their original inspiration. They aren't making Superman look any less "silly" - he's still wearing tights and a cape, for fuck's sake. They're simply making people think about Superman's penis now, and not everybody wants to. And most of all, they're needlessly changing the look of a character known around the world, by all ages and races and sexes, for nearly a century… as wearing his underwear on the outside.
Viva la underpants!