More than anything, it is important to be true to the tone and values of the characters history while presenting them in a modern way. Beyond this, moviegoers rarely care much if there are some minor changes to make the film more in line with contemporary expectations. Few people cared when Burton's Joker killed Batman's parents because it worked within the film. Virtually nobody cared when Nolan completely altered the Harvey Dent character in TDK because it worked within the context of the film. On the flip side, A LOT of people cared when Clark was a mopey, smile free, Edward Cullen wannabe in MAN OF STEEL and his Superman cared more about hurdling tankers and posing in front of the explosion than saving anyone. The film made bank opening weekend because it had a modern, flashy look, but the outraged fans really hurts legs. Bryan Singer's Superman Returns featured a character portrayal much closer to the sincere goodness of the character, but presented it with a gloomy, weird, retro vibe that didn't fit with the mid 2000s whatsoever, and it suffered financially because of it.
I will forever maintain that draft 2 of the Abrams script was an excellent mix of 2000s action cinema while staying largely true to the character and tone of Superman. Draft 1 has its highs and lows as everyone knows. Draft 2 dumped "Luthor is kryptonion" and blew up Krypton while keeping the epic action traditional character riffs. The cast of Anthony Hopkins as Jor-el, Robert Downey Jr as Lex Luthor, and Joel Egerton as Zod-like original character Ty-Zor would be excellent too. Either of McG's favorites Josh Hartnett and Matt Bomer would have been great in the leading role. It is a shame we missed out on it.
Superman: Legacy needs to look and feel fresh and modern, but no doubt it needs to present the characters in ways which are true to their classic selves.