Long Halloween and Hush are really good choices. Out of everyone in DC, I'd say Batman is the easiest to get into.
And I'll vouch for Kingdom Come, as well. That's far and away my favorite comic of all time.
Some personal recommendations:
Superman: Birthright= I'd say the forums are split about 50/50 between the people who like BR and the people who hate it, because Superman's been re-written so many times and everyone has their personal 'definitive' version of him. To me, though, BR is the most new-reader-friendly version, and is just a really good superhero story even if you don't like Superman.
Identity Crisis= This one can be a little bit of a crash-course in DC, but the way everyone's written will make you sympathize with the characters even if you're not immediately familiar with them. It's a really good, really emotional story that hits hard in all the right places.
Justice= Another jump-headfirst-into-everything story, this one is an old-school Silver Age battle royale, showing the Justice League at the height of their power and their first battle against the Legion of Doom. Basically, it's the old Super-Friends cartoon all grown up. Pure awesome.