#14 Justice League Unlimited: The Return
Although Justice League Unlimited's The Return, wasn't really about the Green Lantern Corps, they did play a fairly large role in it. Not only were a slew of Corpsmen showcased, but we finally got to see Kyle Rayner again after his debut way back in the Superman animated series.
Even though it wasn't the Corps who ultimately took down AMAZO, they sure gave it their all and this excellent episode wouldn't have been the same without them.
#25 - Justice League Unlimited: Initiation - John Stewart's new look
#24 - Batman: The Brave and the Bold: Death Race to Oblivion! - Guy Gardner's Lanternmobile
#23 - Justice League of America: Pilot - Doesn't air
#22 - Justice League Unlimited: The Once and Future Thing: Time Warped - Hal Jordan joins the league
#21 - Legends of the Superheroes - Lantern goes live-action
#20 - Justice League: Crisis on Two Earths - Darker shade of green
#19 - Batman Beyond: The Call - Lantern of the future
#18 - Static Shock: Fallen Hero - Hero Worshiped
#17 - Batman: The Brave and the Bold: The Revenge of the Reach! - Loads of Lanterns
#16 - The Batman: Ring Toss - Gotham by Greenlight
#15 - Justice League: Hearts and Minds - More to the Corps
#14 - Justice League Unlimited: The Return - The Corps is Greener Yet