As
Christopher mentions the suspension of disbelief becomes easier for a period piece. Yeah, you can still incorporate some mild sci-fi elements like the comics always have, but you can avoid a lot of complications that contemporary technology brings to the genre.
Part of why I loved
Captain America was because they were able to straddle that line. It was a straight approach with just the right touch of humour and what little camp there was never became denigrating. And Steve Rogers wasn't portrayed as a damaged person. He was a man doing what he really believed was right. He was portrayed very close to how I think a period Superman could be done set in the '40s or '50s. It also generally avoided a hero popping off cynical and smart-ass remarks all the time.