Superman/Batman! It’s the book that got me back into comics after a three year break. Love that series, especially the Loeb run and the Supergirl arc to boot. JSA Classified introduced me to Power Girl and the post-IC Justice League of America was solid too.
The first 12 issues of Gotham Central are on Comixology Unlimited if you have it. Hopefully it gets added here before too long (I would have thought now would be a good time anyway with the last season of Gotham just starting)
Summer of 2001 is when I got back into comics after reading them casually as a kid and a bit more seriously as a teenager. I wasn’t sure where to start, but I vaguely remembered liking Green Lantern so I picked up the current issue of his series.
I was very surprised to see Green Lantern wasn’t Hal Jordan anymore, had a different costume, and wasn’t part of the GLC. So I picked up a couple of early Kyle Rayner trades to get the backstory, one of which costarred Connor Hawke – the new Green Arrow. So that sent me down a rabbit hole learning about how he came to be Green Arrow, and I bought a bunch of back issues of his series. But by this time Kevin Smith had just brought Oliver Queen back to life, so I started buying Green Arrow monthly. Eventually I added Flash and JSA by Geoff Johns, Supergirl by Peter David, and a bunch of other titles to my pull list. I was all in on DC, and I still am.
So for me, the 2000s are the most important decade of DC Comics because that’s when my fandom really started.
All Star Superman
JLA: Tower of Babel
DC The New Frontier
Superman: Red Son
Superman: Birthright
Batman: No Man’s Land
Green Arrow: Year One & Quiver
WW: The Hiketeia
Flash: Blood will Run
Batman: The Black Mirror
Final Crisis