If I had to choose between Superman in jeans and a T-shirt or Superman in flashy armour, I'd take the jeans and T-shirt look. I think Superman in working man clothes is more authentic to the character than Superman in some over-embellished warrior armour. He doesn't need a high-tech outfit, he's Superman.

What the general audience laugh at isn't just trunks over leggings--that's just one detail they focus on--what they're really laughing about is the flamboyant nature of the outfits super-heroes wear. But if you put Tom Welling or Henry Cavill in jeans and a T-shirt, it's easier for the audience to put aside their disbelief and get into the story of an extra-terrestrial raised as a human.