spectacular shocker is right -- when it comes to quality, substantive reprinting of their 1970s and early '80s series, DC has been sadly negligent overall.

1970s -- Look at the Archives for example: Aside from Kamandi and Legion (and ElfQuest which was non-DC material), precious little made it into that deluxe HC format when it came to '70s. A volume or two of Jonah Hex Archives should have made the cut, as an example. Swanderson's Superman got a single slipshodly-produced volume of the ill-fated Comics Classics hardcovers. The current artist-centric books are getting into some of the Batman, etc. from the era, but other work like Flash, World's Finest, JLA (mid-late '70s), Wonder Woman (again mid-late '70s), and much of Superman Family remains unavailable.

1980s -- Amethyst got a very thick Showcase volume. An odd and somewhat ill-advised decision for a series whose coloring was one of its better selling points. Much of 1980s Batman, Superman, Green Lantern, Justice League, etc. all remain out of print without much hope on the horizon. This material includes the work of some greats including Don Newton, whose work on Shazam! STILL is waiting to be collected, and Gene Colan, whose take on Wonder Woman deserves a new look. It would be nice to see more of the work of Joe Kubert and Gil Kane as well, both of whom did quite a lot for DC in the '80s.

Finally, there really needs to be an effort to collect more of the backup material from Dollar Comics series by character, as mentioned for Shazam! A good start would be Mr. & Mrs. Superman, sublime work by Kurt Schaffenberger. Although this and some of the other stuff I've mentioned has nothing to do with omnibus format, it just goes to show how far behind DC has fallen.