Well, it's hard to say. Most of these shows are so twisty and turny, so full of deaths and big consequences, that there are any number of moments that could be considered "important."
But what were the moments that made us stand up and cheer, or stare at the screen in disbelief? Here's our picks:
Honorable Mention: Ra's al Ghul revealed
This one is somewhat dulled becuase we've been expecting him so long, so there wasn't much surprise. Similarly, the big showdown with Oliver that ended 2014 was a bit of a downer only because Ra's managed to make it look so easy.
We didn't get to see Jim Corrigan turn into The Spectre in 2015...but there was probably not a moment that made me pump my fist harder than seeing Zed's vision of things to come for the intrepid New Orleans cop.
With a little luck, we'll get to see Corrigan make his transformation in the season finale of Constantine, set to air in the spring, which we already know will feature guest appearances by not only Corrigan but Papa Midnite as well.
4. The Penguin Mastermind
Gotham is probably the most wildly uneven of the comic book series released this year. There have been glints of genius in the season, but a lot of disappointing stuff as well. The biggest surprise, though, has been how great Robin Lord Taylor has been as The Penguin...
...and then there was "The Penguin's Umbrella," the episode that really used him to the fullest and proved a game-changer for the series. Besides the fact that the episode was unambiguously the best of the season, featuring an ass-kicking Jim Gordon on a mission, a showdown with Zsasz and more, the final moments gave us a widescreen view of Oswald Cobblepot's plans, showing that he's pulling way more of the strings than anybody had guessed.
There were any number of Agents of S.H.I.E.L.D. moments that could have been used here, but we decided to go with Skye's Terrigenesis in the midesason finale, because it paid off one of the show's longest-running threads.
In the moment, it also gave us one of the series' most heartbreaking losses as well, and set up what's likely to be a major conflict for the second half of the season and possibly beyond by establishing that Raina is, like Skye, an Inhuman.
It says something, certainly, about just how dark The Walking Dead has gone this year that the two big "hell yes" moments weren't about character development, or fostering hope, or any of that. They were the moments when terrible people got their comeuppance.
We couldn't decide between the fall of Terminus itself, though, and the fall of its leadership. The two moments were exciting, badass and important for totally different reasons.
In the season premiere, the show subverted the expectations that Team Rick would be stuck in that boxcar for weeks by having Carol save their butts single-handedly and immediately. It was a crowning moment of awesome for a character who's already had four or five of those in her existence.
Later on, after the Terminus cannibals caught up with Rick's group and ate part of Bob's leg, leaving him outside the church as a threat, Rick went on the offensive, leaving the church to take the fight to Gareth. That moment when Gareth thought he had outsmarted everybody by going after Bob, Carl, Judith and Father Gabriel while the "action hero" cast was out hunting them, though, was short-lived...and the would-be Hunters became the hunted and were dispatched quickly and brutally.
Remember back when Samuel L. Jackson appeared at the end of Iron Man to tell Tony that he was part of a larger universe, and he just didn't know it yet?
That's the feeling fans got in the final moments of The Flash's pilot episode, when it was revealed, in one fell swoop, that Harrison Wells was hiding some huge secrets, including a knowledge of Bruce Wayne and a connection to the Crisis on Infinite Earths.
Time-travel, hinted at in the opening scenes, suddenly seemed like small potatoes next to the potential for widescreen storytelling with Crisis on the table, and even a mention of the man who would be Batman drove fans into a frenzy.