shadowknight2814: Pretty much anything by Alan Moore:
Superman: Whatever happened to the Man of Tomorrow?
http://www.amazon.com/Superman-Whatever-Happened-Man-Tomorrow/dp/1401227317/ref=sr_1_1?ie=UTF8&qid=1372899042&sr=8-1&keywords=superman+for+the+man+who+has+everything I'd second All-Star Superman, but it was a bit hit and miss with some of the stories. It's available in 2 trades. The first volume's exploration of Lex Luthor in prison is still the definitive Lex in my mind. They also made an abridged animated movie, but it cut a bit too much.
Batman: The Killing Joke (Alan Moore again) one of the few time you'll see the Joker as having more dimensions than "psycho-killer".
Batman: The Dark Knight returns: Frank Miller. Under no circumstances read the sequel "The Dark Knight Strikes Again." Seriously, don't.
The New Teen Titans: by Marv Wolfmen
Crises on Infinite Earths: Marvel Wolman
Orion: Walt Simonson. Only the first five issues have been collected, the rest you'd have to get back issues for. 25 issues total, not perfect, but when it's good, it's epic.
Justice League International vol 1-6 by Keith Giffen and JM Demattis (not the other JLI, using the same title by a newer team). Ran the gamut from full out comedy, to political intrigue. Ran out of steam towards the end, but I'd definetly at least recommend the first two volumes. This features lesser known heroes, but does have Batman in it for the first few issues.
There's been two mini-series called Deadshot, about a Batman supervillian,. I enjoyed them both, but they've never been collected and you have to get back issues on them. The first mini is pretty dark and "reaistic", the other is more super-hero ish.
Watchmen: This was THE comic miniseries back in the 80's. Much better than the mediocre movie that came out a few weeks ago.
If you're willing to go off the beaten path of the "big" heroes, also:
Saga of the Swamp Thing vol1-6 (Alan Moore) it's important to read these in order, dark horror, pretty good
And, one final Alan Moore recommendation: Miracleman/Marvelman. It's not a DC book, it was a knock-off of DC-owned Captain Marvel. Very good, but dark, exploration of what being able to turn into a Supehuman does to someone psychologically. Very hard to come by, also very unlikely to be reprinted.
Alan Moore, he is the one that made V for Vendetta right, is it better than the film?