The fact that, when making this game, the developers managed to use Danny Elfman's iconic 'Batman' soundtrack, with various pieces fitting various scenes. It wasn't just thrown in, it was carefully and cleverly used, guaranteed to give every fan of the film a big goofy grin
The opening sequence to the game being a near-perfect recreation of the iconic Batman: The Animated Series opening.
LEGO Batman 2: DC Super Heroes
The trailer for Batman 2: DC Superheroes even has one. After the words "Now the world's greatest heroes must unite to stop them" flash on the screen, a sudden cut to a familiar red-and-blue figure slowly descending from the sky... to John Williams' iconic Superman theme. And then immediately followed up by shots of the Dynamic Duo in action to Danny Elfman's Batman theme.
The launch trailer shows off some genuinely exciting stunts.
Batman scaring off a shark that Joker had sicced on him just by snarling at it, no shark repellent required, is both awesome and hilarious.
Flying with Superman is just all kinds of awesome, largely due to the music switching out to the aforementioned theme. Even more once you realize that the hub is comparable in size to Arkham City, yet you can fly all over the place.
A minor one, but when Batman is investigating Joker's escape, he tells Commissioner Gordon that he's heard rumors of Lex Luthor being "not-so-upstanding". While most people would say things like "that's crazy", Gordon just says Batman might want to tell someone. It shows Gordon trusts Batman enough to know he knows what he's talking about.
After a huge (and presumably directionless) chase scene through the streets of Gotham City, Batman reveals he's used the kryptonite leaking from Luthor's Humongous Mecha to create a giant glowing Joker face visible from orbit. Martian Manhunter gets the signal, and promptly calls in the entire Justice League.
In the movie adaptation, the fight between the League and the mech is pretty cool. Like Green Lantern creating a giant cage around it, or Flash removing all the kryptonite from its power core and loading it on Wonder Woman's invisible plane.
Any time you defeat an enemy as a Kryptonian while under the influence of kryptonite.
LEGO Batman 3: Beyond Gotham
The game's intro shows Batman effortlessly taking out three of the Joker's Mooks while they are thrown into panic by the very sight of the Dark Knight.
In the 2nd Level, Robin and Alfred have to take on a brainwashed Batman, who is tearing up the Batcave using his Power Suit, and then the Batmobile. Yes, Robin and Alfred get a level all to themselves after constantly being the Butt-Monkey (particularly in the former's case).
Robin: You bad guys asked for it! It's underappreciated sidekick time!
The Legion of Doom get one for taking over the Watchtower. How? Well, Martian Manhunter was the only one there, and they had Firefly. Bonus points to Joker for securing the Hall of Justice by taking out Hawkman long before the others arrived.
Superman's Big Damn Heroes moment, effortlessly knocking away a swarm of missiles (one by one) and saving the Dynamic Duo.
Firefly's boss fight against Wonder Woman and Flash. While he loses, the fact that he was able to take both of them on says something. He eventually tries getting back up, too... only for Martian Manhunter to recover and deck him with one punch.
Lex (and Joker in a more passive role) taking on Superman and Batman once again, only this time Lex is outfitted with Powered Armour and ready to take him on.
The Legion and League taking out Brainiac's invading forces.
The final level is full of awesome moments:
Hal ends up fighting a pissed off Sinestro. This is awesome for the former, since he alone is able to buy the other good guys time, and also for the latter since it takes literally every other Lantern there to overwhelm him.
shows off some genuinely exciting stunts.