Batman: The Long Halloween and Dark Victory are very good. They kind of have the same vibe as the cartoon from the 90s, which as big a compliment as you can give Batman, IMO. I'm also really digging Morrison's run, but I know that's not for everyone. If you're into super realistic stuff, I must recommend Gotham Central. That was a great series. Also the current Batgirl comic by Bryan Q. Miller is one of my favorite comics every month.
Superman: All-Star Superman. There are no substitutes.
Justice League: I personally really enjoyed Justice League: Year One. It's out of continuity now, but it's a great story. Grant Morrison's JLA was fantastic. It's collected in six trades (New World Order, American Dreams, Rock of Ages, Strength in Numbers, Justice For All and World War III). Also, while I have very little experience in it, people seem to love Justice League International, which was recently released in trades. It's not the Big 7, nor does it pretend to be. Overall it's a lot of fun and doesn't take itself too seriously.
Hawkman: He is a tough character. There are two main camps in how he should be treated and frequently they are at odds. Geoff Johns had a great run on Hawkman in the middle of the last decade. It was short but good. It also heavily tied in with JSA, which was downright amazing.
The Flash: The Flash was a rather lucky character in the 90s and early 00s. Mark Waid had a stellar run on the title starting with issue #62 and went through 129. He would also occasionally write the one or two issues here and there. Geoff Johns began a run starting with #164 and went through 225. Those stand as some of my favorite comics ever. He made Flash's Rogues Gallery into one rivaling Spider-Man and Batman.
Wonder Woman: I'm really not all that familiar with her. I hear Rucka's run from the 00s was pretty good. It was issues 195-226. I have the first trade. It was good. Not mindblowing, but good.
Green Lantern: I liked Rebirth. Geoff Johns' run is considered the epitome of Green Lantern runs, but I find it rather dry and boring. So, yeah... I like them when they guest star, but not as a main book.
Green Arrow: I know people liked Longbow Hunters, but that wasn't for me. I really liked Kevin Smith's run (yes, the movie director). Quiver and Sounds of Violence. Were just great, light action comics. The Archer's Quest by Brad Meltzer (which follows up Kevin Smith's run) stands as one of my favorite comic arcs of all time, but you need to read at least Quiver first before delving in to this one.
Zatanna: Zee is a character who's always been around, but I can't recall her ever having a staring role for long periods. She had a pretty major role in Identity Crisis. She has some run ins with Batman here and there which you can find in various trades. She also was one of the main characters of Grant Morrison's Reboot of Seven Soldiers of Victory from several years back. I don't recall how that was (because I haven't read it), but I have yet to read a Morrison book I haven't liked.
Legion of Superheroes: Like Hawkman, they tend to get rebooted all the time. I believe this will be their 5th reboot. You have the Silver Age Legion, the Post-Zero Hour Legion, the Threeboot Legion, Post Final Crisis Legion (which is more or less the Silver Age Legion) and now they're rebooting Legion for September. Personally, I really liked the first 14 issues of Mark Waid's Threeboot. As far as I'm concerned that's The Legion for me.