I feel like Marvel's Epic Collection line is the most important undertaking in comics preservation outside of piracy, and it's depressing that DC doesn't have a similarly standardized, affordable line of reprints. Almost every single superhero comic published by Marvel in the 1960s has been reprinted in full-color trade paperback. How much of just the Superman titles from that period are available legally?
There are still gaps at Marvel. For instance, there's sadly little to no call to reprint their western or girls' comics. But even so, they're light years ahead of DC.